Synthesis of TiO2-doped SiO2 composite films and its applications

Indian Academy of Sciences (India)

Wintec

structure of the titanium oxide species in the TiO2-doped SiO2 composite films and the photocatalytic reactiv- ity in order to ... gaku D-max γA diffractometer with graphite mono- chromized ... FT–IR absorption spectra of TiO2-doped SiO2 com-.

Development and Application of Binary Suspensions in the Ternary System Cr2O3-TiO2-Al2O3 for S-HVOF Spraying

Science.gov (United States)

Potthoff, Annegret; Kratzsch, Robert; Barbosa, Maria; Kulissa, Nick; Kunze, Oliver; Toma, Filofteia-Laura

2018-04-01

Compositions in the system Cr2O3-TiO2-Al2O3 are among the most used ceramic materials for thermally sprayed coating solutions. Cr2O3 coatings present good sliding wear resistance; Al2O3 coatings show excellent insulation behavior and TiO2 striking corrosion properties. In order to combine these properties, coatings containing more than one oxide are highly interesting. The conventional spraying process is limited to the availability of binary feedstock powders with defined compositions. The use of suspensions offers the opportunity for tailor-made chemical compositions: within the triangle of Cr2O3-TiO2-Al2O3, each mixture of oxides can be created. Criteria for the selection of raw materials as well as the relevant aspects for the development of binary suspensions in the Cr2O3-TiO2-Al2O3 system to be used as feedstock for thermal spraying are presented. This formulation of binary suspensions required the development of water-based single-oxide suspensions with suitable behavior; otherwise, the interaction between the particles while mixing could lead up to a formation of agglomerates, which affect both the stability of the spray process and the coating properties. For the validation of this formulation procedure, binary Cr2O3-TiO2 and Al2O3-TiO2 suspensions were developed and sprayed using the S-HVOF process. The binary coatings were characterized and discussed in terms of microstructure and microhardness.

Development and Application of Binary Suspensions in the Ternary System Cr2O3-TiO2-Al2O3 for S-HVOF Spraying

Science.gov (United States)

Potthoff, Annegret; Kratzsch, Robert; Barbosa, Maria; Kulissa, Nick; Kunze, Oliver; Toma, Filofteia-Laura

2018-03-01

Compositions in the system Cr2O3-TiO2-Al2O3 are among the most used ceramic materials for thermally sprayed coating solutions. Cr2O3 coatings present good sliding wear resistance; Al2O3 coatings show excellent insulation behavior and TiO2 striking corrosion properties. In order to combine these properties, coatings containing more than one oxide are highly interesting. The conventional spraying process is limited to the availability of binary feedstock powders with defined compositions. The use of suspensions offers the opportunity for tailor-made chemical compositions: within the triangle of Cr2O3-TiO2-Al2O3, each mixture of oxides can be created. Criteria for the selection of raw materials as well as the relevant aspects for the development of binary suspensions in the Cr2O3-TiO2-Al2O3 system to be used as feedstock for thermal spraying are presented. This formulation of binary suspensions required the development of water-based single-oxide suspensions with suitable behavior; otherwise, the interaction between the particles while mixing could lead up to a formation of agglomerates, which affect both the stability of the spray process and the coating properties. For the validation of this formulation procedure, binary Cr2O3-TiO2 and Al2O3-TiO2 suspensions were developed and sprayed using the S-HVOF process. The binary coatings were characterized and discussed in terms of microstructure and microhardness.

Enhanced the hydrophobic surface and the photo-activity of TiO2-SiO2 composites

Science.gov (United States)

Wahyuni, S.; Prasetya, A. T.

2017-02-01

The aim of this research is to develop nanomaterials for coating applications. This research studied the effect of various TiO2-SiO2 composites in acrylic paint to enhance the hydrophobic properties of the substrate. Titanium dioxide containing silica in the range 20-35 mol% has been synthesized using sol-gel route. The XRD’s spectra show that increasing SiO2 content in the composite, decreasing its crystalline properties but increasing the surface area. TiO2-SiO2 composite was dispersed in acrylic paint in 2% composition by weight. The largest contact angle was 70, which produced by the substrate coated with TS-35-modified acrylic paint. This study also investigated the enhanced photo-activity of TiO2-SiO2 modified with poly-aniline. The XRD spectra show that the treatment does not change the crystal structure of TiO2. The photo-activity of the composite was evaluated by degradation of Rhodamine-B with visible light. The best performance of the degradation process was handled by the composite treated with 0.1mL anilines per gram of TiO2-SiO2 composite (TSP-A). On the other side, the contact angle 70 has not shown an excellent hydrophobic activity. However, the AFM spectra showed that nanoroughness has started to form on the surface of acrylic paint modified with TiO2-SiO2 than acrylic alone.

Passivation of pigment-grade TiO2 particles by nanothick atomic layer deposited SiO2 films

International Nuclear Information System (INIS)

King, David M; Liang Xinhua; Weimer, Alan W; Burton, Beau B; Akhtar, M Kamal

2008-01-01

Pigment-grade TiO 2 particles were passivated using nanothick insulating films fabricated by atomic layer deposition (ALD). Conformal SiO 2 and Al 2 O 3 layers were coated onto anatase and rutile powders in a fluidized bed reactor. SiO 2 films were deposited using tris-dimethylaminosilane (TDMAS) and H 2 O 2 at 500 deg. C. Trimethylaluminum and water were used as precursors for Al 2 O 3 ALD at 177 deg. C. The photocatalytic activity of anatase pigment-grade TiO 2 was decreased by 98% after the deposition of 2 nm SiO 2 films. H 2 SO 4 digest tests were performed to exhibit the pinhole-free nature of the coatings and the TiO 2 digest rate was 40 times faster for uncoated TiO 2 than SiO 2 coated over a 24 h period. Mass spectrometry was used to monitor reaction progress and allowed for dosing time optimization. These results demonstrate that the TDMAS-H 2 O 2 chemistry can deposit high quality, fully dense SiO 2 films on high radius of curvature substrates. Particle ALD is a viable passivation method for pigment-grade TiO 2 particles

Sol-gel synthesis of TiO2-SiO2 photocatalyst for β-naphthol photodegradation

International Nuclear Information System (INIS)

Qourzal, S.; Barka, N.; Tamimi, M.; Assabbane, A.; Nounah, A.; Ihlal, A.; Ait-Ichou, Y.

2009-01-01

Silica gel supported titanium dioxide particles (TiO 2 -SiO 2 ) prepared by sol-gel method was as photocatalyst in the degradation of β-naphthol in water under UV-illumination. The prepared sample has been characterized by powder X-ray diffraction (XRD), infrared spectroscopy (IR) and scanning electron microscopy (SEM). The supported catalyst had large surface area and good sedimentation ability. The photodegradation rate of β-naphthol under UV-irradiation depended strongly on adsorption capacity of the catalyst, and the photoactivity of the supported catalyst was much higher than that of the pure titanium dioxides. The experiments were measured by high performance liquid chromatography (HPLC). The photodegradation rate of β-naphthol using 60% TiO 2 -SiO 2 particles was faster than that using TiO 2 'Degussa P-25', TiO 2 'PC-50' and TiO 2 'Aldrich' as photocatalyst by 2.7, 4 and 7.8 times, respectively. The kinetics of photocatalytic β-naphthol degradation was found to follow a pseudo-first-order rate law. The effect of the TiO 2 loading on the photoactivity of TiO 2 -SiO 2 particles was also discussed. With good photocatalytic activity under UV-irradiation and the ability to be readily separated from the reaction system, this novel kind of catalyst exhibited the potential effective in the treatment of organic pollutants in aqueous systems.

Visible Light Excited Catalysis and Reusability Performances of TiO2@Pr:Y2SiO5 Upconversion Materials

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Yan Jiao

2017-01-01

Full Text Available To get high efficiency photodegradation on pollutants under visible light, Pr(III doped Y2SiO5 upconversion materials and anatase TiO2 nanofilm coated Pr:Y2SiO5 composite have been prepared by using a sol-gel method. XRD and SEM test results indicated that TiO2 nanofilm was well coated on Pr:Y2SiO5 to form TiO2@Pr:Y2SiO5 composite particles with the sizes of 0.5–1.0 μm. To avoid secondary pollution resulting from incomplete recovery of catalyst particles, TiO2@Pr:Y2SiO5 was loaded on the glass fiber filters by using a dip-coating method. It is found that the catalyst particles were embedded into the carrier firmly, even after having been reused for 6 times. The luminescence intensities of TiO2@Pr:Y2SiO5 were getting down sharply with the coating contents of TiO2 increased, which was attributed to the adsorption of the luminescence by the TiO2 film in situ. As a result, TiO2@Pr:Y2SiO5 with 4% TiO2, which presented lowest luminescence intensity, showed the highest efficiency on the photodegradation of nitrobenzene wastewater. The catalysts loaded on glass fiber filters showed excellent reusability on the photodegradation of nitrobenzene and presented a photodegradation rate of 95% at the first time and up to 75.9% even after 6 times of reusing by the treatment time of 12 h.

NOx photocatalytic degradation on gypsum plates modified by TiO2-N,C photocatalysts

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Janus Magdalena

2015-09-01

Full Text Available In presented studies the photocatalytic decomposition of NOx on gypsum plates modified by TiO2-N,Cphotocatalysts were presented. The gypsum plates were obtained by addition of 10 or 20 wt.% of different types of titanium dioxide, such as: pure TiO2 and carbon and nitrogen co-modified TiO2 (TiO2-N,C to gypsum. TiO2-N,C photocatalysts were obtained by heating up the starting TiO2 (Grupa Azoty Zakłady Chemiczne Police S.A in the atmosphere of ammonia and carbon at the temperature: 100, 300 i 600ºC. Photocatalyst were characterized by FTIR/DRS, UVVis/DR, BET and XRD methods. Moreover the compressive strength tests of modified gypsum were also done. Photocatalytic activity of gypsum plates was done during NOx decomposition. The highest photocatalytic activity has gypsum with 20 wt.% addition of TiO2-N,C obtained at 300ºC.

The Effect of SiO2 Shell on the Suppression of Photocatalytic Activity of TiO2 and ZnO Nanoparticles

International Nuclear Information System (INIS)

Lee, Min Hee; Lee, Choon Soo; Patil, Umakant Mahadev; Kochuveedu, Saji Thomas

2012-01-01

In this study, we investigate the potential use of TiO 2 SiO 2 and ZnO SiO 2 core/shell nanoparticles (NPs) as effective UV shielding agent. In the typical synthesis, SiO 2 was coated over different types of TiO 2 (anatase and rutile) and ZnO by sol-gel method. The synthesized TiO 2 SiO 2 and ZnO SiO 2 Nps were characterized by UV-Vis, XRD, Sem and TEM. The UV-vis absorbance and transmittance spectra of core shell NPs showed an efficient blocking effect in the UV region and more than 90% transmittance in the visible region. XRD and SAED studies confirmed the formation of amorphous SiO 2 coated over the TiO 2 and ZnO NPs. The FESEM and TEM images shows that coating of SiO 2 over the surface of anatase, rutile TiO 2 and ZnO NPs resulted in the increase in particle size by ∼30 nm. In order to study the UV light shielding capability of the samples, photocatalytic degradation of methylene blue dye on TiO 2 SiO 2 and ZnO SiO 2 NPs was performed. Photocatalytic activity for both types of TiO 2 NPs was partially suppressed. In comparison, the photocatalytic activity of ZnO almost vanished after the SiO 2 coating

Cotton fabric finishing with TiO2/SiO2 composite hydrosol based on ionic cross-linking method

International Nuclear Information System (INIS)

Xu, Z.J.; Tian, Y.L.; Liu, H.L.; Du, Z.Q.

2015-01-01

Highlights: • We studied the cotton finishing with TiO 2 /SiO 2 based on ionic cross-linking method. • The samples treated with CHTAC had lower value of whiteness. • The samples treated with BTCA achieved higher crease recovery angle and lower tensile strength. • The ionic cross-linking treatment (CHTAC + BTCA + TiO 2 /SiO 2 ) was better than with TiO 2 /SiO 2 sol alone. - Abstract: Cotton fabric was successfully modified by 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CHTAC), 1,2,3,4-butanetetracarboxylic acid (BTCA) and TiO 2 /SiO 2 sol. Self-cleaning characteristic was investigated using a Color Measuring and Matching System with 6 h sunlight irradiation. And the stability of TiO 2 /SiO 2 coatings was explored by measuring the washing fastness and wrinkle resistance of treated cotton samples. In addition, whiteness index, crease recovery angle and tensile strength retention (%) of treated samples were evaluated. Moreover, the morphology, structure change and crystallinity of samples were observed by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD), respectively. The results revealed that the samples treated with CHTAC had lower value of whiteness index as compared with original cotton fabric. It was also found that samples treated with BTCA achieved higher crease recovery angle and lower tensile strength. Moreover, the treatment of CHTAC and BTCA had adverse effect on the crystallinity of cotton samples, as treated samples had lower crystallinity in comparison with raw cotton fabrics. Nevertheless, the stability of self-cleaning coatings was better for samples treated with ionic cross-linking treatment (CHTAC + BTCA + TiO 2 /SiO 2 ) than samples treated with TiO 2 /SiO 2 sol alone. Furthermore, compared with original samples the UV-blocking property of ionic cross-linking treated samples was obviously enhanced

Facile fabrication of Si-doped TiO2 nanotubes photoanode for enhanced photoelectrochemical hydrogen generation

Science.gov (United States)

Dong, Zhenbiao; Ding, Dongyan; Li, Ting; Ning, Congqin

2018-04-01

Photoelectrochemical (PEC) water splitting based doping modified one dimensional (1D) titanium dioxide (TiO2) nanostructures provide an efficient method for hydrogen generation. Here we first successfully fabricated 1D Si-doped TiO2 (Ti-Si-O) nanotube arrays through anodizing Ti-Si alloys with different Si amount, and reported the PEC properties for water splitting. The Ti-Si-O nanotube arrays fabricated on Ti-5 wt.% Si alloy and annealed at 600 °C possess higher PEC activity, yielding a higher photocurrent density of 0.83 mA/cm2 at 0 V vs. Ag/AgCl. The maximum photoconversion efficiency was 0.54%, which was 2.7 times the photoconversion efficiency of undoped TiO2.

Optical properties of ZrO2, SiO2 and TiO2-SiO2 xerogels and coatings doped with Eu3+ and Eu2+

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Gonçalves Rogéria R.

1999-01-01

Full Text Available Eu3+ doped bulk monoliths and thin films were obtained by sol-gel methods in the ZrO2, SiO2 and SiO2-TiO2 systems. Eu3+ 5D0 ® 7FJ emission and decay time characteristics were measured during the entire experimental preparation route from the initial sol to the final xerogels. The crystalline phases identified were tetragonal ZrO2 and mixtures of rutile and anatase TiO2 at high temperature treatments in bulk samples. Good quality thin films were obtained for all systems by dip-coating optical glasses (Schott BK270. The same spectroscopic features were observed either for the bulk monoliths or the films. By appropriate heat treatments under H2 atmosphere Eu2+ containing samples could be obtained in the SiO2-TiO2 system.

Co-electrospinning fabrication and photocatalytic performance of TiO2/SiO2 core/sheath nanofibers with tunable sheath thickness

International Nuclear Information System (INIS)

Cao, Houbao; Du, Pingfan; Song, Lixin; Xiong, Jie; Yang, Junjie; Xing, Tonghai; Liu, Xin; Wu, Rongrong; Wang, Minchao; Shao, Xiaoli

2013-01-01

Graphical abstract: - Highlights: • The core–sheath TiO 2 /SiO 2 nanofibers were fabricated by co-electrospinning technique. • The catalytic property of nanofibers with different sheath thickness was studied. • The potential methods of improving catalytic efficiency are suggested. - Abstract: In this paper, core/sheath TiO 2 /SiO 2 nanofibers with tunable sheath thickness were directly fabricated via a facile co-electrospinning technique with subsequent calcination at 500 °C. The morphologies and structures of core/sheath TiO 2 /SiO 2 nanofibers were characterized by TGA, FESEM, TEM, FTIR, XPS and BET. It was found that the 1D core/sheath nanofibers are made up of anatase–rutile TiO 2 core and amorphous SiO 2 sheath. The influences of SiO 2 sheath and its thickness on the photoreactivity were evaluated by observing photo-degradation of methylene blue aqueous solution under the irradiation of UV light. Compared with pure TiO 2 nanofibers, the core/sheath TiO 2 /SiO 2 nanofibers performed a better catalytic performance. That was attributed to not only efficient separation of hole–electron pairs resulting from the formation of heterojunction but also larger surface area and surface silanol group which will be useful to provide higher capacity for oxygen adsorption to generate more hydroxyl radicals. And the optimized core/sheath TiO 2 /SiO 2 nanofibers with a sheath thickness of 37 nm exhibited the best photocatalytic performance

Photocatalytic Degradation of Chlorobenzene by TiO2 in High-Temperature and High-Pressure Water

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N. Kometani

2008-01-01

Full Text Available A fluidized-bed-type flow reactor available for the photocatalytic treatment of the suspension of model soil under high-temperature, high-pressure conditions was designed. An aqueous suspension containing hydrogen peroxide (H2O2 as an oxidizer and inorganic oxides as a model soil, titania (TiO2, silica (SiO2, or kaoline (Al2Si2O5(OH4 was continuously fed into the reactor with the temperature and the pressure controlled to be T=20–400∘C and P = 30 MPa, respectively. The degradation of chlorobenzene (CB in water was chosen as a model oxidation reaction. It appeared that most of the model soils are not so harmful to the SCWO treatment of CB in solutions. When the TiO2 suspension containing H2O2 was irradiated with near-UV light, the promotion of the degradation caused by photocatalytic actions of TiO2 was observed at all temperatures. Persistence of the photocatalytic activity in the oxidation reaction in high-temperature, high-pressure water would open up a possibility of the development of the hybrid process based on the combination of SCWO process and TiO2 photocatalysis for the treatment of environmental pollutants in soil and water, which are difficult to handle by conventional SCWO process or catalytic SCWO process alone.

Enhancement of photocatalytic properties of TiO2 nanoparticles doped with CeO2 and supported on SiO2 for phenol degradation

International Nuclear Information System (INIS)

Hao, Chunjing; Li, Jing; Zhang, Zailei; Ji, Yongjun; Zhan, Hanhui; Xiao, Fangxing; Wang, Dan; Liu, Bin; Su, Fabing

2015-01-01

Highlights: • CeO 2 -TiO 2 /SiO 2 composites were prepared via a facile co-precipitation method. • Introduction of SiO 2 support increases the dispersion of CeO 2 -TiO 2 . • CeO 2 -TiO 2 /SiO 2 exhibits an enhanced photocatalytic efficiency for phenol degradation. • Ce 3+ /Ce 4+ pair coexisting in CeO 2 improves electron–hole pairs separation efficiency. - Abstract: A series of CeO 2 -TiO 2 and CeO 2 -TiO 2 /SiO 2 composites were prepared with TiCl 4 and Ce (NO 3 ) 3 ·6H 2 O as precursors via a facile co-precipitation method. The obtained samples were characterized by various techniques such as X-ray diffraction (XRD), nitrogen adsorption (N 2 -BET), Fourier transformation infrared spectrum (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and UV–Vis spectroscopy measurements. The results indicated that TiO 2 doped with CeO 2 and supported on SiO 2 could reduce the crystallite size, inhibit the phase transformation, enhance the thermal stability, and effectively extend the spectral response from UV to visible range. When applied to the phenol photodegradation on a homemade batch reactor with an external cooling jacket, the CeO 2 -TiO 2 /SiO 2 catalysts exhibited significantly enhanced photodegradation efficiency in comparison with commercial Degussa P25 and CeO 2 -TiO 2 . The unique catalytic properties of CeO 2 -TiO 2 /SiO 2 were ascribed to improved electron–hole pairs separation efficiency and formation of more reactive oxygen species owing to the presence of Ce 3+ /Ce 4+ , as well as high dispersion of active component of CeO 2 -TiO 2 as a result of the introduction of SiO 2 support. Furthermore, the catalysts can be easily recovered from the reaction solution by centrifugation and reused for four cycles without significant loss of activity

Comparison Study on the Microstructure of Nanocrystalline TiO2 in Different Ti-Si Binary Oxides

Institute of Scientific and Technical Information of China (English)

无

2007-01-01

Three different Ti-Si oxide structuares, silica supported titania, silica coated titania and intimately mixed silicatitania, containing 10%-40% SiO2, were made by sol-gel process. The variations of microstructure parameters of nanocrystalline (nc) TiO2-anatase in the three kirds of binary oxides, including in-plane spacing d, cell constants (a0, CQ), cell volume V, cell axial ratio c0/a0 and crystal grain size, were comparatively investigated by high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). It is found that the microstructure parameters vary remarkably with increasing SiO2 content and annealing temperature. Different structured Ti-Si binary oxides lead to different variation tendencies of microstructure parameters. The more SiO2 the binary oxide contains, the more lattice defects of nc TiO2-anatase appear; diffusion or migration of Si cations could be an important influential factor in the variations of microstructure. The grain size of nc TiO2 in the three kinds of binary oxides not only depends on SiO2 content and annealing temperature but also on the degree of lattice microstrain and distortion of nc TiO2-anatase. Both grain size and phase transformation of nc TiO2-anatase are effectively inhibited with increasing SiOa content.

The photovoltaic impact of atomic layer deposited TiO2 interfacial layer on Si-based photodiodes

Science.gov (United States)

Karabulut, Abdulkerim; Orak, İkram; Türüt, Abdulmecit

2018-06-01

In present work, photocurrent, current-voltage (I-V) and capacitance/conductance-voltage-frequency (C/G-V-f) measurements were analyzed for the photodiode and diode parameters of Al/TiO2/p-Si structure. The TiO2 thin film structure was deposited on p-Si by using atomic layer deposition technique (ALD) and its thickness was about 10 nm. The surface morphology of TiO2 coated on p-Si structure was observed via atomic force microscope (AFM). Barrier height (Φb) and ideality factor (n) values of device were found to be 0.80 eV, 0.70 eV, 0.56 eV and 1.04, 2.24, 10.27 under dark, 10 and 100 mW/cm2, respectively. Some photodiodes parameters such as fill factor (FF), power efficiency (%η), open circuit voltage (Voc), short circuit current (Isc) were obtained from I-V measurement under different light intensity. FF and η were accounted 49.2, 39,0 and 0.05, 0.45 under 10 and 100 mW/cm2 light power intensity, respectively. C-2-V graph was plotted from C-V-f measurements and zero bias voltage (V0), donor concentration (Nd), Fermi energy (EF), barrier height (Φb) and maximum electric field (Em) were determined from C-2-V data for different frequencies. The electrical and photocurrent values demonstrated that it can be used for photodiode, photo detector and photo sensing applications.

Above room temperature ferromagnetism in Si:Mn and TiO(2-delta)Co.

Science.gov (United States)

Granovsky, A; Orlov, A; Perov, N; Gan'shina, E; Semisalova, A; Balagurov, L; Kulemanov, I; Sapelkin, A; Rogalev, A; Smekhova, A

2012-09-01

We present recent experimental results on the structural, electrical, magnetic, and magneto-optical properties of Mn-implanted Si and Co-doped TiO(2-delta) magnetic oxides. Si wafers, both n- and p-type, with high and low resistivity, were used as the starting materials for implantation with Mn ions at the fluencies up to 5 x 10(16) cm(-2). The saturation magnetization was found to show the lack of any regular dependence on the Si conductivity type, type of impurity and the short post-implantation annealing. According to XMCD Mn impurity in Si does not bear any appreciable magnetic moment at room temperature. The obtained results indicate that above room temperature ferromagnetism in Mn-implanted Si originates not from Mn impurity but rather from structural defects in Si. The TiO(2-delta):Co thin films were deposited on LaAlO3 (001) substrates by magnetron sputtering in the argon-oxygen atmosphere at oxygen partial pressure of 2 x 10(-6)-2 x 10(-4) Torr. The obtained transverse Kerr effect spectra at the visible and XMCD spectra indicate on intrinsic room temperature ferromagnetism in TiO(2-delta):Co thin films at low (< 1%) volume fraction of Co.

Crystallization behaviour of nanostructured hybrid SiO2-TiO2 gel glasses to nanocomposites.

Science.gov (United States)

Tsvetelina, Gerganova; Yordanka, Ivanova; Yuliya, Vueva; Miranda, Salvado Isabel M; Helena, Fernandes Maria

2010-04-01

The crystallization behaviour of hybrid SiO2-TiO2 nanocomposites derived from titanosiloxanes by sol-gel method has been investigated depending on the type of siloxane precursor and the pirolysis temperature. The resulting hybrid titanosiloxanes, crosslinked with trimethylsilil isocyanate (nitrogen-modified) or methyltrietoxisilane (carbon-modified), were pirolyzed in an inert atmosphere in the temperature range between 600 to 1100 degrees C in order to form C-(N)-Si-O-TiO2 nanocomposites. By means of XRD, FTIR, 29Si NMR, SEM, TEM and AFM investigations have been established that the transformation of the nanostructured SiO2-TiO2 hybrid materials into nanocomposites as well as the crystalline size depend on the titanium content and the type of cross-linking agents used in the synthesizes.

Probing properties of the interfacial perimeter sites in TiO x /Au/SiO 2 with 2-propanol decomposition

Energy Technology Data Exchange (ETDEWEB)

Wu, Yi Y.; Kung, Harold H. (NWU)

2017-11-01

The decomposition of 2-propanol was studied over SiO2, SiO2 with an overlayer of TiO2 (Ti/SiO2), Au/SiO2, and Au/SiO2 with an overlayer of TiO2 (Ti/[Au/SiO2]) at 170–190 °C. There was no reaction on SiO2. Propene was the only product on Ti/SiO2, and its rate of formation increased proportionally with the Ti content. Acetone was the major product (selectivity 65–99%) on all Au-containing catalysts. Its rate of formation also increased with Ti loading. In addition, small amounts of propene were also formed on Ti/[Au/SiO2] the rate of which increased with Ti loading. Characterization of the catalysts with N2 adsorption, STEM, DR-UV-vis spectroscopy, XPS, XANES and EXAFS suggested that the Ti formed an amorphous TiO2 overlayer on the catalyst. At high Ti loadings (4–5 wt.%), there were patches of thick porous TiO2 layer, and some microdomains of crystalline TiO2 could be detected. Au was present as 1–3 nm nanoparticles on all catalysts, before and after used in reaction. Only Lewis acid sites were detected based on results from pyridine adsorption, and their quantities increased with Ti loading. Based on the comparison of reaction rates, the dependence of the kinetics on 2-propanol partial pressure, the apparent activation energies, and the effect of co-feeding O2 among different catalysts, it was concluded that propene was formed on the TiO2 overlayer, acetone was formed primarily at the Au-TiO2 interfacial perimeter sites, and α-C-H bond breaking preceding acetone formation was more facile on Au at the interfacial site than other surface Au atoms. Implication of these results to the selective acetone formation in the oxidation of propane in the presence of a O2/H2 mixture was discussed.

Alkali passivation mechanism of sol-gel derived TiO2-SiO2 films coated on soda-lime-silica glass substrates

Energy Technology Data Exchange (ETDEWEB)

Matsuda, A; Matsuno, Y; Katayama, S; Tsuno, T [Nippon Steel Glass Co. Ltd., Tokyo (Japan); Toge, N; Minami, T [University of Osaka Prefecture, Osaka (Japan). College of Engineering

1992-09-01

TiO2-SiO2 films prepared by the sol-gel method serves as an effective alkali passivation layer on a soda-lime-silica glass substrate and the film is superior to a sol-gel derived pure SiO2 film from the view point of weathering resistance improvement. To clarify the reason, alkali passivation mechanism of sol-gel derived TiO2-SiO2 glass films with different TiO2 contents coated on a soda-lime-silica glass substrate was studied by SIMS (secondary ion mass spectroscopy) and XPS (X-ray photoelectron spectroscopy) analyses, and compared with the results of a sol-gel derived pure SiO2 film. As a result, the following conclusions were obtained: An increase in TiO2 content in the TiO2 SiO2 film increases the sodium concentration in the film, which was induced by sodium migration from the glass substrate during the heat-treatment. Because of the presence of sodium the TiO2 -SiO2 films serve not as a barrier but as an effective getter of alkali ions and thereby effectively improve the weathering resistance Of the glass substrate. 10 refs., 6 figs.

Synthesis of hybrid cellulose nanocomposite bonded with dopamine SiO2/TiO2 and its antimicrobial activity

Science.gov (United States)

Ramesh, Sivalingam; Kim, Gwang-Hoon; Kim, Jaehwan; Kim, Joo-Hyung

2015-04-01

Organic-inorganic hybrid material based cellulose was synthesized by the sol-gel approach. The explosion of activity in this area in the past decade has made tremendous progress in industry or academic both fundamental understanding of sol-gel process and applications of new functionalized hybrid materials. In this present research work, we focused on cellulose-dopamine functionalized SiO2/TiO2 hybrid nanocomposite by sol-gel process. The cellulose-dopamine hybrid nanocomposite was synthesized via γ-aminopropyltriethoxysilane (γ-APTES) coupling agent by in-situ sol-gel process. The chemical structure of cellulose-amine functionalized dopamine bonding to cellulose structure with covalent cross linking hybrids was confirmed by FTIR spectral analysis. The morphological analysis of cellulose-dopamine nanoSiO2/TiO2 hybrid nanocomposite materials was characterized by XRD, SEM and TEM. From this different analysis results indicate that the optical transparency, thermal stability, control morphology of cellulose-dopamine-SiO2/TiO2 hybrid nanocomposite. Furthermore cellulose-dopamine-SiO2/TiO2 hybrid nanocomposite was tested against pathogenic bacteria for antimicrobial activity.

Synthesis variables effect on TiO2/polyester fabrics photoactivity and stability

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Camilo Castro

2016-12-01

Full Text Available TiO2-SiO2 coatings on fabric samples were obtained by immersion of 9cm2 of commercial polyester in a TiO2-SiO2 suspension. This suspension was prepared by adding TiO2 P25 to a silica matrix obtained from the hydrolysis of tetraethyl orthosilicate (TEOS. The aim of this work was to study the relationship between the immersion time of the fabric on the photocatalytic activity and stability of the coating against several cycles of use and washing. Obtained samples were characterized by scanning electron microscopy (SEM, energy dispersive spectroscopy (EDS and infrared spectroscopy (FTIR-ATR. Evaluation of modified fabrics was performed by self-disinfection tests under 250W/m2 of simulated sunlight using E. coli as model bacteria. In general, all modified fabrics (except that obtained at 2h immersion time inactivated bacteria in less than 120min and its regrowth was prevented for at least 24h after the disinfection tests. It was determined that low immersion time (3-4h lead to active and stable fabrics to 3 cycles of use and washing, whereas higher immersion times (12h lead to more active but unstable fabrics.

The effect of rare earth dopants on the structure, surface texture and photocatalytic properties of TiO2-SiO2 prepared by sol-gel method

International Nuclear Information System (INIS)

Mohamed, R.M.; Mkhalid, I.A.

2010-01-01

The sol-gel method was successfully used to prepare a series of TiO 2 -SiO 2 and rare earth (RE) (La 3+ , Nd 3+ , Sm 3+ , Gd 3+ )-doped TiO 2 -SiO 2 nanoparticles at a doping level of 3 atomic percent. The structural features of parent TiO 2 -SiO 2 and RE-TiO 2 -SiO 2 fired at 550 o C have been investigated by XRD, UV-diffuse reflection, SEM and nitrogen adsorption measurements at -196 o C. XRD data verified the formation of typical characteristic anatase form in all the prepared RE-doped TiO 2 -SiO 2 samples. In comparison with the pure TiO 2 -SiO 2 samples (ca. 35 nm in diameter), the RE-TiO 2 -SiO 2 samples have relatively small particle size indicating that the doping with RE metal ions can improve the particle morphology, and retard the grain growth of TiO 2 -SiO 2 during heat treatment. The results indicated that Gd 3+ doped TiO 2 -SiO 2 has the lowest bandgap and particle size compared with pure TiO 2 -SiO 2 and other nanoparticles of RE-doped TiO 2 -SiO 2 . The highest surface area (S BET ) and pore volume (V p ) values were recorded for Gd-TiO 2 -SiO 2 as well. The effect of doping on the photoactivity was evaluated by the photocatalytic degradation of EDTA as a probe reaction. Among all the pure and RE-doped TiO 2 -SiO 2 , Gd 3+ -TiO 2 -SiO 2 performed the highest catalytic activity towards the tested reaction. That might be due to its special characteristics of particle size, surface texture and bandgap properties. Details of the synthesis procedure and results of the characterization studies of the produced RE-TiO 2 -SiO 2 are presented in this paper.

Preparation of TiO2-SiO2 composite photocatalysts for environmental applications

Czech Academy of Sciences Publication Activity Database

Paušová, Š.; Krýsa, J.; Jirkovský, Jaromír; Prevot, V.; Mailhot, G.

2014-01-01

Roč. 89, č. 8 (2014), s. 1129-1135 ISSN 0268-2575 Institutional support: RVO:61388955 Keywords : photocatalysis * TiO2/SiO2 * composite Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.349, year: 2014

Photocatalytic Removal of Phenol under Natural Sunlight over N-TiO2-SiO2 Catalyst: The Effect of Nitrogen Composition in TiO2-SiO2

Directory of Open Access Journals (Sweden)

Viet-Cuong Nguyen

2009-01-01

Full Text Available In this present work, high specific surface area and strong visible light absorption nitrogen doped TiO2-SiO2 photocatalyst was synthesized by using sol-gel coupled with hydrothermal treatment method. Nitrogen was found to improve the specific surface area while it also distorted the crystal phase of the resulting N-TiO2-SiO2 catalyst. As the N/ (TiO2-SiO2 molar ratio was more than 10%, the derived catalyst presented the superior specific surface area up to 260 m2/g. Nevertheless, its photoactivity towards phenol removal was observed to significantly decrease, which could results from the too low crystallinity. The nitrogen content in N-TiO2-SiO2 catalyst was therefore necessary to be optimized in terms of phenol removal efficiency and found at ca. 5%. Under UVA light and natural sunlight irradiation of 80 min, N(5%-TiO2-SiO2 catalyst presented the phenol decomposition efficiencies of 68 and 100%, respectively. It was also interestingly found in this study that the reaction rate was successfully expressed using a Langmuir-Hinshelwood (L-H model, indicating the L-H nature of photocatalytic phenol decomposition reaction on the N-TiO2-SiO2 catalyst.

Comparative differences in the behavior of TiO2 and SiO2 food additives in food ingredient solutions

Science.gov (United States)

Yusoff, Ridhwan; Nguyen, Luong T. H.; Chiew, Paul; Wang, Zheng Ming; Ng, Kee Woei

2018-03-01

Nanotechnology is widely used in the food industry to improve the color, taste, and texture of food products. However, concerns regarding potential undesirable health effects remain. It is expected that interaction of engineered nanomaterials (ENMs) with food ingredients will influence their behavior and the resulting corona. Nonetheless, there are limited systematic studies conducted to clarify this understanding to date. Herein, we investigated the behavior and corona formation of food grade titanium dioxide (TiO2) and silicon dioxide (SiO2) in solutions of model food ingredients including bovine serum albumin (BSA) and sucrose. Measurements using dynamic light scattering (DLS) showed that both TiO2 and SiO2 nanoparticles displayed a decrease in agglomerate sizes in the presence of both food ingredients. Both particles were negatively charged in all the conditions tested. Corona adsorption studies were carried out using multiple complementary methods including Fourier transform infrared (FTIR) spectroscopy, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF-MS), transmission electron microscopy (TEM), micro bicinchoninic acid (BCA) protein assay, and thermogravimetric analysis (TGA). Comparative investigation showed that sucrose could disperse both particles more effectively than BSA and that SiO2 displayed greater adsorption capacity for both BSA and sucrose, compared to TiO2. Taken collectively, this study demonstrated the importance of considering food ingredient effects when mapping the behavior of ENMs in food products. Such understanding could be significant in the evaluation of biological effects, such as toxicity, of ENMs used in food products.

Investigating the solubility and cytocompatibility of CaO-Na2 O-SiO2 /TiO2 bioactive glasses.

Science.gov (United States)

Wren, Anthony W; Coughlan, Aisling; Smith, Courtney M; Hudson, Sarah P; Laffir, Fathima R; Towler, Mark R

2015-02-01

This study aims to investigate the solubility of a series of titanium (TiO2 )-containing bioactive glasses and their subsequent effect on cell viability. Five glasses were synthesized in the composition range SiO2 -Na2 O-CaO with 5 mol % of increments TiO2 substituted for SiO2 . Glass solubility was investigated with respect to (1) exposed surface area, (2) particle size, (3) incubation time, and (4) compositional effects. Ion release profiles showed that sodium (Na(+) ) presented high release rates after 1 day and were unchanged between 7 and 14 days. Calcium (Ca(2+) ) release presented a significant change at each time period and was also composition dependent, where a reduction in Ca(2+) release is observed with an increase in TiO2 concentration. Silica (Si(4+) ) release did not present any clear trends while no titanium (Ti(4+) ) was released. Cell numbers were found to increase up to 44%, compared to the growing control population, with a reduction in particle size and with the inclusion of TiO2 in the glass composition. © 2014 Wiley Periodicals, Inc.

Seed-mediated photodeposition route to Ag-decorated SiO2@TiO2 microspheres with ideal core-shell structure and enhanced photocatalytic activity

Science.gov (United States)

Ma, Jianqi; Guo, Xiaohua; Ge, Hongguang; Tian, Guanghui; Zhang, Qiang

2018-03-01

Ag-decorated SiO2@TiO2 microspheres (SiO2@TiO2-Ag) with ideal core-shell structure and enhanced photocatalytic activity were successfully fabricated by combining both coating anatase TiO2 on the surface of SiO2 spheres and subsequent depositing face-centered cubic Ag nanoparticles (NPs) on the coated TiO2 surface via novel sol-gel method and Ag-seed-mediated photodeposition (PD) route, respectively. The morphology, structure, composition and optical properties of the resulting composites were characterized in detail. The results reveal that the monodisperse SiO2 spheres of ∼260 nm were covered uniformly and perfectly by the TiO2 nanoparticle coating layer with the thickness of ca. 55 nm by the novel sol-gel method. Further, homogeneously and highly dispersed Ag NPs with an average size of 8 ± 1.5 nm were strongly anchored onto the TiO2 surface in SiO2@TiO2 core-shell spheres by the modified PD process (Ag-seed-mediated PD route), whereas polydispersed Ag aggregates and detached Ag NPs were irregularly deposited over the TiO2 surface in previous works, which is the inherent problem and has not been effectively solved for depositing noble metal NPs such as Au, Ag, Pt, Pd on TiO2 surface by conventional PD method. The formation mechanism of small and uniformly dispersed Ag NPs with narrow size distribution via the modified PD method is tentatively explained by both nucleation kinetics and growth kinetics. The key reason is that the pre-deposited seeds firmly tethered on SiO2@TiO2 spheres served as nucleation sites and anchoring points for the further nucleation and subsequent growth of Ag via photoreduction of Ag+.

Design and Synthesis of Hierarchical SiO2@C/TiO2 Hollow Spheres for High-Performance Supercapacitors.

Science.gov (United States)

Zhang, Ying; Zhao, Yan; Cao, Shunsheng; Yin, Zhengliang; Cheng, Li; Wu, Limin

2017-09-06

TiO 2 has been widely investigated as an electrode material because of its long cycle life and good durability, but the relatively low theoretical capacity restricts its practical application. Herein, we design and synthesize novel hierarchical SiO 2 @C/TiO 2 (HSCT) hollow spheres via a template-directed method. These unique HSCT hollow spheres combine advantages from both TiO 2 such as cycle stability and SiO 2 with a high accessible area and ionic transport. In particular, the existence of a C layer is able to enhance the electrical conductivity. The SiO 2 layer with a porous structure can increase the ion diffusion channels and accelerate the ion transfer from the outer to the inner layers. The electrochemical measurements demonstrate that the HSCT-hollow-sphere-based electrode manifests a high specific capacitance of 1018 F g -1 at 1 A g -1 which is higher than those for hollow TiO 2 (113 F g -1 ) and SiO 2 /TiO 2 (252 F g -1 ) electrodes, and substantially higher than those of all the previously reported TiO 2 -based electrodes.

Enhanced PEC performance of nanoporous Si photoelectrodes by covering HfO2 and TiO2 passivation layers

Science.gov (United States)

Xing, Zhuo; Ren, Feng; Wu, Hengyi; Wu, Liang; Wang, Xuening; Wang, Jingli; Wan, Da; Zhang, Guozhen; Jiang, Changzhong

2017-03-01

Nanostructured Si as the high efficiency photoelectrode material is hard to keep stable in aqueous for water splitting. Capping a passivation layer on the surface of Si is an effective way of protecting from oxidation. However, it is still not clear in the different mechanisms and effects between insulating oxide materials and oxide semiconductor materials as passivation layers. Here, we compare the passivation effects, the photoelectrochemical (PEC) properties, and the corresponding mechanisms between the HfO2/nanoporous-Si and the TiO2/nanoporous-Si by I-V curves, Motte-schottky (MS) curves, and electrochemical impedance spectroscopy (EIS). Although the saturated photocurrent densities of the TiO2/nanoporous Si are lower than that of the HfO2/nanoporous Si, the former is more stable than the later.

Enhanced PEC performance of nanoporous Si photoelectrodes by covering HfO2 and TiO2 passivation layers.

Science.gov (United States)

Xing, Zhuo; Ren, Feng; Wu, Hengyi; Wu, Liang; Wang, Xuening; Wang, Jingli; Wan, Da; Zhang, Guozhen; Jiang, Changzhong

2017-03-02

Nanostructured Si as the high efficiency photoelectrode material is hard to keep stable in aqueous for water splitting. Capping a passivation layer on the surface of Si is an effective way of protecting from oxidation. However, it is still not clear in the different mechanisms and effects between insulating oxide materials and oxide semiconductor materials as passivation layers. Here, we compare the passivation effects, the photoelectrochemical (PEC) properties, and the corresponding mechanisms between the HfO 2 /nanoporous-Si and the TiO 2 /nanoporous-Si by I-V curves, Motte-schottky (MS) curves, and electrochemical impedance spectroscopy (EIS). Although the saturated photocurrent densities of the TiO 2 /nanoporous Si are lower than that of the HfO 2 /nanoporous Si, the former is more stable than the later.

Fabrication and tritium release property of Li2TiO3-Li4SiO4 biphasic ceramics

Science.gov (United States)

Yang, Mao; Ran, Guangming; Wang, Hailiang; Dang, Chen; Huang, Zhangyi; Chen, Xiaojun; Lu, Tiecheng; Xiao, Chengjian

2018-05-01

Li2TiO3-Li4SiO4 biphasic ceramic pebbles have been developed as an advanced tritium breeder due to the potential to combine the advantages of both Li2TiO3 and Li4SiO4. Wet method was developed for the pebble fabrication and Li2TiO3-Li4SiO4 biphasic ceramic pebbles were successfully prepared by wet method using the powders synthesized by hydrothermal method. The tritium release properties of the Li2TiO3-Li4SiO4 biphasic ceramic pebbles were evaluated. The biphasic pebbles exhibited good tritium release property at low temperatures and the tritium release temperature was around 470 °C. Because of the isotope exchange reaction between H2 and tritium, the addition of 0.1%H2 to purge gas He could significantly enhance the tritium gas release and the fraction of molecular form of tritium increased from 28% to 55%. The results indicate that the Li2TiO3-Li4SiO4 biphasic ceramic pebbles fabricated by wet method exhibit good tritium release property and hold promising potential as advanced breeder pebbles.

Reflection Enhancement Using TiO2/SiO2 Bilayer Films Prepared by Cost-Effective Sol-gel Method

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R. Ajay Kumar

2017-04-01

Full Text Available Multilayer dielectric thin film structure has been demanded for its application in optoelectronic devices such as optical waveguides, vertical cavity surface-emitting devices, biosensors etc. In this paper, we present the fabrication and characterization of bilayer thin films of TiO2/SiO2 using sol-gel spin coating method. Ellipsometer measurement showed refractive index values 1.46, 2.1 corresponding to the SiO2 and TiO2 films respectively. The FTIR transmittance peaks observed at ~970 cm-1, ~1100 cm-1 and ~1400 cm-1 are attributed to the Ti-O-Si, Si-O-Si and Ti-O-Ti bonds respectively. Maximum reflectance is observed from two bilayer film structure which can be further optimized to get the high reflection to a broad wavelength range.

Multifunctional Roles of TiO 2 Nanoparticles for Architecture of Complex Core−Shells and Hollow Spheres of SiO 2 −TiO 2 −Polyaniline System

KAUST Repository

Wang, Dan Ping

2009-10-27

Nanoparticles are often used as seeds to grow one-dimensional nanomaterials or as core materials to prepare core-shell nanostructures. On the other hand, the presynthesized inorganic nanoparticles can also be used as starting building blocks to prepare inorganic-polymer nanocomposites. In this work, we explore the roles of metal-oxide nanoparticles (anatase TiO2) in the area of constructional synthesis of highly complex core-shell and hollow sphere nanostructures comprising SiO2, TiO2, and polyaniline (PAN). In particular, multifunctional roles of oleate-surfactant-protected TiO2 nanoparticles have been revealed in this study: they provide starting sites for polymerization of aniline on the surface of SiO2 mesospheres; they land on the inner surface of polyaniline shell to form a secondary material phase; they work as initial crystalline seeds for homogeneous growth of interior TiO2 shell; and they serve as primary nanobuilding blocks to form exterior TiO2 shell on the polyaniline via self-assembly. With the assistance of the TiO2 nanoparticles, a total of six complex core-shell and hollow sphere nanocomposites (SiO 2/TiO2, SiO2/TiO2/PAN, SiO 2/TiO2/PAN/TiO2, TiO2/PAN, TiO 2/PAN/TiO2, and TiO2/TiO2) have been made in this work through controlled self-assembly, templating growth, polymerization, and homogeneous seeded growth. Applicability of these nanostructures in photocatalytic applications has also been demonstrated by our preliminary investigations. The easy separation of used catalysts after reaction seems to be advantageous because of relatively large external diameters of the lightweight nanocomposites. © 2009 American Chemical Society.

Annealing of TiO2 Films Deposited on Si by Irradiating Nitrogen Ion Beams

International Nuclear Information System (INIS)

Yokota, Katsuhiro; Yano, Yoshinori; Miyashita, Fumiyoshi

2006-01-01

Thin TiO2 films were deposited on Si at a temperature of 600 deg. C by an ion beam assisted deposition (IBAD) method. The TiO2 films were annealed for 30 min in Ar at temperatures below 700 deg. C. The as-deposited TiO2 films had high permittivities such 200 εo and consisted of crystallites that were not preferentially oriented to the c-axis but had an expanded c-axis. On the annealed TiO2 films, permittivities became lower with increasing annealing temperature, and crystallites were oriented preferentially to the (110) plane

Theoretical prediction of Grüneisen parameter for SiO_2.TiO_2 bulk metallic glasses

International Nuclear Information System (INIS)

Singh, Chandra K.; Pandey, Brijesh K.; Pandey, Anjani K.

2016-01-01

The Grüneisen parameter (γ) is very important to decide the limitations for the prediction of thermoelastic properties of bulk metallic glasses. It can be defined in terms of microscopic and macroscopic parameters of the material in which former is based on vibrational frequencies of atoms in the material while later is closely related to its thermodynamic properties. Different formulation and equation of states are used by the pioneer researchers of this field to predict the true sense of Gruneisen parameter for BMG but for SiO_2.TiO_2 very few and insufficient information is available till now. In the present work we have tested the validity of two different isothermal EOS viz. Poirrior-Tarantola EOS and Usual-Tait EOS to predict the true value of Gruneisen parameter for SiO_2.TiO_2 as a function of compression. Using different thermodynamic limitations related to the material constraints and analyzing obtained result it is concluded that the Poirrior-Tarantola EOS gives better numeric values of Grüneisen parameter (γ) for SiO_2.TiO_2 BMG.

Microwave-assisted synthesis and characterization of poly(acrylic)/SiO2-TiO2 core-shell nanoparticle hybrid thin films

International Nuclear Information System (INIS)

Chien, Wen-Chen; Yu, Yang-Yen; Chen, Po-Kan; Yu, Hui-Huan

2011-01-01

In this study, poly(acrylic)/SiO 2 -TiO 2 core-shell nanoparticle hybrid thin films were successfully synthesized by microwave-assisted polymerization. The coupling agent 3-(trimethoxysilyl) propyl methacrylate (MSMA) was hydrolyzed with colloidal SiO 2 -TiO 2 core-shell nanoparticles, and then polymerized with two acrylic monomers and initiator to form a precursor solution. The results of this study showed that the spin-coated hybrid films had relatively good surface planarity, high thermal stability, a tunable refractive index (1.525 2 -TiO 2 core-shell nanoparticle hybrid thin films, for potential use in optical applications.

Gel electrolytes based on poly(acrylonitrile)/sulpholane with hybrid TiO2/SiO2 filler for advanced lithium polymer batteries

International Nuclear Information System (INIS)

Kurc, Beata

2014-01-01

Highlights: • Paper describes properties of gel electrolyte based on PAN with TMS and TiO 2 -SiO 2 . • The TiO 2 -SiO 2 oxide composite was precipitated in the emulsion system and used as the fillers. • The capacity of the graphite anode depends on the current rate and the amount of TiO 2 -SiO 2 . • For PE3 electrolyte was obtained practical capacity more than 90% of the theoretical capacity. - Abstract: This paper describes the synthesis and properties of a new type of ceramic fillers for composite polymer gel electrolytes. Hybrid TiO 2 -SiO 2 ceramic powders have been obtained by co-precipitation from titanium(IV) sulfate solution using sodium silicate as the precipitating agent. The resulting submicron-size powders have been applied as fillers for composite polymer gel electrolytes for Li-ion batteries based on polyacrylonitrile (PAN) membranes. The powders and gel electrolytes have been examined structurally and electrochemically, showing favorable properties in terms of electrolyte uptake and electrochemical characteristics in Li-ion cells

Whiter, brighter, and more stable cellulose paper coated with TiO2 /SiO2 core/shell nanoparticles using a layer-by-layer approach.

Science.gov (United States)

Cheng, Fei; Lorch, Mark; Sajedin, Seyed Mani; Kelly, Stephen M; Kornherr, Andreas

2013-08-01

To inhibit the photocatalytic degradation of organic material supports induced by small titania (TiO2 ) nanoparticles, four kinds of TiO2 nanoparticles, that is, commercial P25-TiO2 , commercial rutile phase TiO2 , rutile TiO2 nanorods and rutile TiO2 spheres, prepared from TiCl4 , were coated with a thin, but dense, coating of silica (SiO2 ) using a conventional sol-gel technique to form TiO2 /SiO2 core/shell nanoparticles. These core/shell particles were deposited and fixed as a very thin coating onto the surface of cellulose paper samples by a wet-chemistry polyelectrolyte layer-by-layer approach. The TiO2 /SiO2 nanocoated paper samples exhibit higher whiteness and brightness and greater stability to UV-bleaching than comparable samples of blank paper. There are many potential applications for this green chemistry approach to protect cellulosic fibres from UV-bleaching in sunlight and to improve their whiteness and brightness. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

TiO2 coated Si nanowire electrodes for electrochemical double layer capacitors in room temperature ionic liquid

International Nuclear Information System (INIS)

Konstantinou, F; Shougee, A; Albrecht, T; Fobelets, K

2017-01-01

Three TiO 2 deposition processes are used to coat the surface of Si nanowire array electrodes for electrochemical double layer capacitors in room temperature ionic liquid [Bmim][NTF 2 ]. The fabrication processes are based on wet chemistry only and temperature treatments are kept below 450 °C. Successful TiO 2 coatings are found to be those that are carried out at low pressure and with low TiO 2 coverage to avoid nanowires breakage. The best TiO 2 coated Si nanowire array electrode in [Bmim][NTF 2 ] showed energy densities of 0.9 Wh·kg −1 and power densities of 2.2 kW·kg −1 with a nanowire length of ∼10 µ m. (paper)

Catalytic combustion of trichloroethylene over TiO2-SiO2 supported catalysts

NARCIS (Netherlands)

Kulazynski, M.; van Ommen, J.G.; Trawczynski, J.; Walendziewski, J.

2002-01-01

Combustion of trichloroethylene (TCE) on Cr2O3, V2O5, Pt or Pd catalysts supported on TiO2-SiO2 as a carrier has been investigated. It was found that oxide catalysts are very active but their activity quickly diminishes due to loss of the active component, especially at higher reaction temperatures

High-temperature interaction in the ZrSiO4-TiO2 system

International Nuclear Information System (INIS)

Matveeva, F.A.; Melekhova, T.F.; Samsonova, T.I.

1976-01-01

The solid phase interaction in the ZrSiO 4 - TiO 2 system in the region of lower concentrations of TiO 2 (between 0-30%) when heating in the range 1400-1600 0 C is investigated. The different mechanism of the interaction of zircon and titanium dioxide with a content of titanium dioxide of 10% and higher is shown. In compounds with a TiO 2 content to 10%, a solid solution of titanium dioxide and zircon arises, with a limiting value of TiO 2 dissolving in zircon of 1% at 1400 0 C and 2% at 1500-1600 0 C. The partial decomposition of zircon giving crystobalite and the solid solution of separated zirconium dioxide with rutile occurs when the content of titanium dioxide is higher than 10%

Efectos de fotodegradación propiciados por recubrimientos de TiO2 y TiO2-SiO2 obtenidos por Sol-Gel

Directory of Open Access Journals (Sweden)

Rodriguez Paez, J. E.

2008-10-01

Full Text Available Photodegradation effect is widely used for water purification this contributes to preservation and protection of environment. Titanium oxide, (TiO2, is a compound that shows up this phenomenon. TiO2 is a semiconductor which may degradate pollutants through of a oxidation process. It permit the treatment of the residual water. It this work we has conformed coatings of TiO2 y TiO2-SiO2, utilized Sol-Gel method and investigated the degradation of the blue Methylene. For this, we introduced these coatings in the blue methylene solution which was illuminated with radiation of λ=365nm to activate its photocatilist properties. The structures of the coatings were characterized using Atomic Force Microscopy (AFM and X-ray Photoelectron Spectroscopy (XPS.El efecto de fotodegradación es ampliamente utilizado para la purificación del agua, acción que contribuye a la conservación y protección del medio ambiente; el óxido de titanio (TiO2 es uno de los semiconductores que pueden degradar contaminantes mediante procesos de oxidación, lo que lo hace apto para el tratamiento de aguas residuales. En este trabajo se conformaron recubrimientos de TiO2 y TiO2-SiO2, por el método Sol-Gel, y se estudio la degradación que experimentaba una solución de azul de metileno al introducirle estos recubrimientos e iluminarlos con una radiación de λ=365nm para activar su propiedad fotocatalítica. Los recubrimientos fueron caracterizados microestructuralmente utilizando Microscopía de Fuerza Atómica (MFA y Espectroscopía de Fotoelectrones de rayos X (XPS. Los resultados obtenidos de los ensayos de fotodegradación indican que los recubrimientos con una cantidad pequeña de silicio presentan un mayor efecto de fotodegradación indicando que el silicio puede generar puntos de anclaje que facilitan las reacciones de fotocatálisis. Por otro lado, la formación de centros activos, constituidos principalmente por carbono, también contribuyeron al desarrollo de estas

Resistance Switching Memory Characteristics of Si/CaF2/CdF2 Quantum-Well Structures Grown on Metal (CoSi2) Layer

Science.gov (United States)

Denda, Junya; Uryu, Kazuya; Watanabe, Masahiro

2013-04-01

A novel scheme of resistance switching random access memory (ReRAM) devices fabricated using Si/CaF2/CdF2/CaF2/Si quantum-well structures grown on metal CoSi2 layer formed on a Si substrate has been proposed, and embryonic write/erase memory operation has been demonstrated at room temperature. It has been found that the oxide-mediated epitaxy (OME) technique for forming the CoSi2 layer on Si dramatically improves the stability and reproducibility of the current-voltage (I-V) curve. This technology involves 10-nm-thick Co layer deposition on a protective oxide prepared by boiling in a peroxide-based solution followed by annealing at 550 °C for 30 min for silicidation in ultrahigh vacuum. A switching voltage of lower than 1 V, a peak current density of 32 kA/cm2, and an ON/OFF ratio of 10 have been observed for the sample with the thickness sequence of 0.9/0.9/2.5/0.9/5.0 nm for the respective layers in the Si/CaF2/CdF2/CaF2/Si structure. Results of surface morphology analysis suggest that the grain size of crystal islands with flat surfaces strongly affects the quality of device characteristics.

Silicon electrodeposition from chloride-fluoride melts containing K2SiF6 and SiO2

Directory of Open Access Journals (Sweden)

Zhuk Sergey I.

2017-01-01

Full Text Available Silicon electrodeposition on glassy carbon from the KF-KCl-K2SiF6, KF-KCl-K2SiF6-KOH and KF-KCl-K2SiF6-SiO2 melts was studied by the cyclic voltammetry. Тhe electroreduction of Si(IV to metallic Si was observed as a single 4-electron wave under all considered conditions. The reactions of cathode reduction of silicon from fluoride and oxyfluoride complexes were suggested. It was shown that the process can be controlled by the preliminary transformation of SiO44- to SiF62- and SiOxFyz-. The influence of the current density on structure and morphology of silicon deposits obtained during galvanostatic electrolysis of the KF-KCl-K2SiF6-SiO2 melt was studied.

Optical properties of amorphous SiO2-TiO2 multi-nanolayered coatings for 1064-nm mirror technology

Science.gov (United States)

Magnozzi, M.; Terreni, S.; Anghinolfi, L.; Uttiya, S.; Carnasciali, M. M.; Gemme, G.; Neri, M.; Principe, M.; Pinto, I.; Kuo, L.-C.; Chao, S.; Canepa, M.

2018-01-01

The use of amorphous, SiO2-TiO2 nanolayered coatings has been proposed recently for the mirrors of 3rd-generation interferometric detectors of gravitational waves, to be operated at low temperature. Coatings with a high number of low-high index sub-units pairs with nanoscale thickness were found to preserve the amorphous structure for high annealing temperatures, a key factor to improve the mechanical quality of the mirrors. The optimization of mirror designs based on such coatings requires a detailed knowledge of the optical properties of sub-units at the nm-thick scale. To this aim we have performed a Spectroscopic Ellipsometry (SE) study of amorphous SiO2-TiO2 nanolayered films deposited on Si wafers by Ion Beam Sputtering (IBS). We have analyzed films that are composed of 5 and 19 nanolayers (NL5 and NL19 samples) and have total optical thickness nominally equivalent to a quarter of wavelength at 1064 nm. A set of reference optical properties for the constituent materials was obtained by the analysis of thicker SiO2 and TiO2 homogeneous films (∼ 120 nm) deposited by the same IBS facility. By flanking SE with ancillary techniques, such as TEM and AFM, we built optical models that allowed us to retrieve the broad-band (250-1700 nm) optical properties of the nanolayers in the NL5 and NL19 composite films. In the models which provided the best agreement between simulation and data, the thickness of each sub-unit was fitted within rather narrow bounds determined by the analysis of TEM measurements on witness samples. Regarding the NL5 sample, with thickness of 19.9 nm and 27.1 nm for SiO2 and TiO2 sub-units, respectively, the optical properties presented limited variations with respect to the thin film counterparts. For the NL19 sample, which is composed of ultrathin sub-units (4.4 nm and 8.4 nm for SiO2 and TiO2, respectively) we observed a significant decrease of the IR refraction index for both types of sub-units; this points to a lesser mass density with

A promising tritium breeding material: Nanostructured 2Li2TiO3-Li4SiO4 biphasic ceramic pebbles

Science.gov (United States)

Dang, Chen; Yang, Mao; Gong, Yichao; Feng, Lan; Wang, Hailiang; Shi, Yanli; Shi, Qiwu; Qi, Jianqi; Lu, Tiecheng

2018-03-01

As an advanced tritium breeder material for the fusion reactor blanket of the International Thermonuclear Experimental Reactor (ITER), Li2TiO3-Li4SiO4 biphasic ceramic has attracted widely attention due to its merits. In this paper, the uniform precursor powders were prepared by hydrothermal method, and nanostructured 2Li2TiO3-Li4SiO4 biphasic ceramic pebbles were fabricated by an indirect wet method at the first time. In addition, the composition dependence (x/y) of their microstructure characteristics and mechanical properties were investigated. The results indicated that the crush load of biphasic ceramic pebbles was better than that of single phase ceramic pebbles under identical conditions. The 2Li2TiO3-Li4SiO4 ceramic pebbles have good morphology, small grain size (90 nm), satisfactory crush load (37.8 N) and relative density (81.8 %T.D.), which could be a promising breeding material in the future fusion reactor.

Cotton fabric coated with nano TiO2-acrylate copolymer for photocatalytic self-cleaning by in-situ suspension polymerization

International Nuclear Information System (INIS)

Jiang Xue; Tian Xiuzhi; Gu Jian; Huang Dan; Yang Yiqi

2011-01-01

Two kinds of nano TiO 2 -polyacrylate hybrid dispersions, TBM-w and TBM-e were synthesized by in-situ suspension polymerization and solution polymerization respectively, in order to fix the nano TiO 2 on fabrics. The photocatalytic self-cleaning fabrics have received much attention in recent years for its water-saving and environment-protection advantages. However, the fixation of the photocatalyst on fabrics is still a key problem that inhibits industrialization of these eco-friendly fabrics. The cotton fabric was treated by the two hybrid dispersions. The photocatalytic self-cleaning property was characterized. Infrared spectroscopy, burning loss test and thermogravimetry showed that some copolymer chains entangled with the nano TiO 2 . Transmission electron microscope illustrated that there was a polymeric layer on the surface of nano TiO 2 . The average diameter of TBM-w was smaller than that of TBM-e based on size analysis. The photocatalytic decoloration of the grape syrup indicated that the fabric with TiO 2 -polymer hybrid had excellent self-cleaning property.

TiO2 (NanoParticles Extracted from Sugar-Coated Confectionery

Directory of Open Access Journals (Sweden)

Martina Lorenzetti

2017-01-01

Full Text Available As the debate about TiO2 food additive safety is still open, the present study focuses on the extraction and characterisation of TiO2 (nanoparticles added as a whitening agent to confectionary products, that is, chewing gum pellets. The aim was to (1 determine the colloidal properties of suspensions mutually containing TiO2 and all other chewing gum ingredients in biologically relevant media (preingestion conditions; (2 characterise the TiO2 (nanoparticles extracted from the chewing gum coating (after ingestion; and (3 verify their potential photocatalysis. The particle size distribution, in agreement with the zeta potential results, indicated that a small but significant portion of the particle population retained mean dimensions close to the nanosize range, even in conditions of moderate stability, and in presence of all other ingredients. The dispersibility was enhanced by proteins (i.e., albumin, which acted as surfactants and reduced particle size. The particle extraction methods involved conventional techniques and no harmful chemicals. The presence of TiO2 particles embedded in the sugar-based coating was confirmed, including 17–30% fraction in the nanorange (<100 nm. The decomposition of organics under UV irradiation proved the photocatalytic activity of the extracted (nanoparticles. Surprisingly, photocatalysis occurred even in presence of an amorphous SiO2 layer surrounding the TiO2 particles.

Removal of binary azo dyes from water by UV-irradiated degradation in TiO2 suspensions

International Nuclear Information System (INIS)

Juang, Ruey-Shin; Lin, Su-Hsia; Hsueh, Pei-Ying

2010-01-01

Photodegradation and mineralization of single and binary Acid Orange 7 (AO7) and Reactive Red 2 (RR2) under UV irradiation in TiO 2 suspensions was examined. Experiments were conducted as a function of initial pH, TiO 2 dose, and initial dye concentration. First-order derivative spectrophotometric method was used to simultaneously analyze AO7 and RR2 in binary solutions. The Langmuir-Hinshelwood kinetic model was applied to evaluate and compare the apparent rate constants for the photodegradation of both dyes in single and binary solutions. It was shown that photodegradation of both dyes in binary solution was slower than those in single solution under comparable conditions. Moreover, the difference between the apparent rate constants of RR2 and AO7 became smaller in contrast to the cases of single solutions. After 20-min UV irradiation with 0.5 g/L TiO 2 , complete removal of single 0.086 mM AO7 and 0.086 mM RR2 at pH 6.8 was obtained, but only 60% and 45% of binary 0.086 mM AO7 and 0.086 mM RR2 was removed, respectively.

High photocatalytic activity of hierarchical SiO2@C-doped TiO2 hollow spheres in UV and visible light towards degradation of rhodamine B.

Science.gov (United States)

Zhang, Ying; Chen, Juanrong; Hua, Li; Li, Songjun; Zhang, Xuanxuan; Sheng, Weichen; Cao, Shunsheng

2017-10-15

Ongoing research activities are targeted to explore high photocatalytic activity of TiO 2 -based photocatalysts for the degradation of environmental contaminants under UV and visible light irradiation. In this work, we devise a facile, cost-effective technique to in situ synthesize hierarchical SiO 2 @C-doped TiO 2 (SCT) hollow spheres for the first time. This strategy mainly contains the preparation of monodisperse cationic polystyrene spheres (CPS), sequential deposition of inner SiO 2 , the preparation of the sandwich-like CPS@SiO 2 @CPS particles, and formation of outer TiO 2 . After the one-step removal of CPS templates by calcination at 450°C, hierarchical SiO 2 @C-doped TiO 2 hollow spheres are in situ prepared. The morphology, hierarchical structure, and properties of SCT photocatalyst were characterized by TEM. SEM, STEM Mapping, BET, XRD, UV-vis spectroscopy, and XPS. Results strongly confirm the carbon doping in the outer TiO 2 lattice of SCT hollow spheres. When the as-synthesized SCT hollow spheres were employed as a photocatalyst for the degradation of Rhodamine B under visible-light and ultraviolet irradiation, the SCT photocatalyst exhibits a higher photocatalytic activity than commercial P25, effectively overcoming the limitations of poorer UV activity for many previous reported TiO 2 -based photocatalysts due to doping. Copyright © 2017 Elsevier B.V. All rights reserved.

Performance of NiFe2O4-SiO2-TiO2 Magnetic Photocatalyst for the Effective Photocatalytic Reduction of Cr(VI in Aqueous Solutions

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Mike O. Ojemaye

2017-01-01

Full Text Available Investigation into the reduction of Cr(VI in aqueous solution was carried out through some batch photocatalytic studies. The photocatalysts used were silica coated nickel ferrite nanoparticles (NiFe2O4-SiO2, nickel ferrite titanium dioxide (NiFe2O4-TiO2, nickel ferrite silica titanium dioxide (NiFe2O4-SiO2-TiO2, and titanium dioxide (TiO2. The characterization of the materials prepared via stepwise synthesis using coprecipitation and sol-gel methods were carried out with the aid of X-ray diffraction (XRD, transmission electron microscopy (TEM, scanning electron microscopy (SEM, Fourier transform infrared (FTIR spectroscopy, thermal gravimetric analysis (TGA, and vibrating sample magnetometry (VSM. The reduction efficiency was studied as a function of pH, photocatalyst dose, and contact time. The effects of silica interlayer between the magnetic photocatalyst materials reveal that reduction efficiency of NiFe2O4-SiO2-TiO2 towards Cr(VI was higher than that of NiFe2O4-TiO2. However, TiO2 was observed to have the highest reduction efficiency at all batch photocatalytic experiments. Kinetics study shows that photocatalytic reduction of Cr(VI obeyed Langmuir-Hinshelwood model and first-order rate kinetics. Regenerability study also suggested that the photocatalyst materials can be reused.

Preparación y propiedades de materiales cerámicos bioinertes en el sistema Al2O3-TiO2-SiO2

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Boccaccini, A. R.

1998-12-01

Full Text Available Very fine and sinterable ceramic powders (100-600 nm in the system Al2O3-TiO2-SiO2 were obtained by the method of cohydrolisis from organo-metallic precursors. Isostatically pressed powder compacts could be densified to a relative high density (~ 92 % th. density at relative low temperatures (1320-1380ºC. The technical coefficient of thermal expansion was measured by dilatometry. The value obtained (8.8 10-6 1/ºC corresponds closely to that of Ti, opening the possibility to use Al2O3-TiO2-SiO2 ceramics to fabricate metal/ceramic composite implants. The measured mechanical properties of dense sintered Al2O3-TiO2-SiO2 material: Young´s modulus, flexure strength and compression strength, are higher than those of pure TiO2. Highly porous Al2O3-TiO2-SiO2 ceramics (P~ 65% were obtained by the method of evaporation of hydrogen peroxide. These materials exhibited interconnected porosity and their properties, particularly the Young´s modulus, resulted very similar to those of bone, which is an important pre-requisite for the design of quirurgical implants.Se han obtenido polvos cerámicos muy finos (100- 600 nm y de alta sinterabilidad, en el sistema Al2O3-TiO2-SiO2, por el método de co-hidrólisis controlada a partir de precursores organo-metálicos. Los compactos fabricados a partir del polvo de cohidrólisis calcinado fueron sinterizados en el rango de temperaturas 1320-1380 ºC, obteniéndose densidades elevadas (~ 92% D.T.. El coeficiente de expansión térmica técnico del material cerámico sinterizado fue medido por dilatometría. El valor obtenido, 8.8 10-6 ºC-1, es muy similar al de titanio metálico y por lo tanto el material cerámico Al2O3-TiO2-SiO2 puede ser candidato para la fabricación de implantes compuestos cerámico/metal. Las propiedades mecánicas: módulo de elasticidad, resistencia a la flexión y resistencia a la compresión, del material denso sinterizado, fueron determinadas, resultando muy superiores a las de TiO2 puro

Effects of deposition rates on laser damage threshold of TiO2/SiO2 high reflectors

International Nuclear Information System (INIS)

Yao Jianke; Xu Cheng; Ma Jianyong; Fang Ming; Fan Zhengxiu; Jin Yunxia; Zhao Yuanan; He Hongbo; Shao Jianda

2009-01-01

TiO 2 single layers and TiO 2 /SiO 2 high reflectors (HR) are prepared by electron beam evaporation at different TiO 2 deposition rates. It is found that the changes of properties of TiO 2 films with the increase of rate, such as the increase of refractive index and extinction coefficient and the decrease of physical thickness, lead to the spectrum shift and reflectivity bandwidth broadening of HR together with the increase of absorption and decrease of laser-induced damage threshold. The damages are found of different morphologies: a shallow pit to a seriously delaminated and deep crater, and the different amorphous-to-anatase-to-rutile phase transition processes detected by Raman study. The frequency shift of Raman vibration mode correlates with the strain in film. Energy dispersive X-ray analysis reveals that impurities and non-stoichiometric defects are two absorption initiations resulting to the laser-induced transformation.

Highly uniform bipolar resistive switching characteristics in TiO2/BaTiO3/TiO2 multilayer

International Nuclear Information System (INIS)

Ma, W. J.; Zhang, X. Y.; Wang, Ying; Zheng, Yue; Lin, S. P.; Luo, J. M.; Wang, B.; Li, Z. X.

2013-01-01

Nanoscale multilayer structure TiO 2 /BaTiO 3 /TiO 2 has been fabricated on Pt/Ti/SiO 2 /Si substrate by chemical solution deposition method. Highly uniform bipolar resistive switching (BRS) characteristics have been observed in Pt/TiO 2 /BaTiO 3 /TiO 2 /Pt cells. Analysis of the current-voltage relationship demonstrates that the space-charge-limited current conduction controlled by the localized oxygen vacancies should be important to the resistive switching behavior. X-ray photoelectron spectroscopy results indicated that oxygen vacancies in TiO 2 play a crucial role in the resistive switching phenomenon and the introduced TiO 2 /BaTiO 3 interfaces result in the high uniformity of bipolar resistive switching characteristics

Cellulose acetate-based SiO2/TiO2 hybrid microsphere composite aerogel films for water-in-oil emulsion separation

Science.gov (United States)

Yang, Xue; Ma, Jianjun; Ling, Jing; Li, Na; Wang, Di; Yue, Fan; Xu, Shimei

2018-03-01

The cellulose acetate (CA)/SiO2-TiO2 hybrid microsphere composite aerogel films were successfully fabricated via water vapor-induced phase inversion of CA solution and simultaneous hydrolysis/condensation of 3-aminopropyltrimethoxysilane (APTMS) and tetrabutyl titanate (TBT) at room temperature. Micro-nano hierarchical structure was constructed on the surface of the film. The film could separate nano-sized surfactant-stabilized water-in-oil emulsions only under gravity. The flux of the film for the emulsion separation was up to 667 L m-2 h-1, while the separation efficiency was up to 99.99 wt%. Meanwhile, the film exhibited excellent stability during multiple cycles. Moreover, the film performed excellent photo-degradation performance under UV light due to the photocatalytic ability of TiO2. Facile preparation, good separation and potential biodegradation maked the CA/SiO2-TiO2 hybrid microsphere composite aerogel films a candidate in oil/water separation application.

High Photocatalytic Performance of Two Types of Graphene Modified TiO2 Composite Photocatalysts

Science.gov (United States)

Zhang, Jun; Li, Sen; Tang, Bo; Wang, Zhengwei; Ji, Guojian; Huang, Weiqiu; Wang, Jinping

2017-07-01

High quality and naturally continuous structure of three-dimensional graphene network (3DGN) endow it a promising candidate to modify TiO2. Although the resulting composite photocatalysts display outstanding performances, the lacking of active sites of the 3DGN not only goes against a close contact between the graphene basal plane and TiO2 nanoparticles (weaken electron transport ability) but also limits the efficient adsorption of pollutant molecules. Similar with surface functional groups of the reduced graphene oxide (RGO) nanosheets, surface defects of the 3DGN can act as the adsorption sites. However, the defect density of the 3DGN is difficult to control (a strict cool rate of substrate and a strict flow of precursor gas are necessary) because of its growth approach (chemical vapor deposition method). In this study, to give full play to the functions of graphene, the RGO nanosheets and 3DGN co-modified TiO2 composite photocatalysts are prepared. After optimizing the mass fraction of the RGO nanosheets in the composite photocatalyst, the resulting chemical adsorption ability and yields of strong oxidizing free radicals increase significantly, indicating the synergy of the RGO nanosheets and 3DGN.

Photocatalytic activity of Ti3+ self-doped dark TiO2 ultrafine nanorods, grey SiO2 nanotwin crystalline, and their composite under visible light

Science.gov (United States)

Zhang, Renhui; Yang, Yingchang; Leng, Senlin; Wang, Qing

2018-04-01

Efficient electron-holes separation is of crucial importance for the improvement of photocatalytic activity for photocatalytic reaction. In this work, dark TiO2 (D-TiO2) nanorods, grey SiO2 (G-SiO2) and D-TiO2/G-SiO2 composite with surface defects are synthesized. We report that the efficiency of photo-generated electrons and holes separation is well enhanced by introducing G-SiO2 into D-TiO2 lattice. Using first-principles method, we find that surface defects (O or Si vacancy) can be conducive to improving the optical absorption under visible-light region. Combination of the experimental results, for D-TiO2/G-SiO2 composite, the surface defects of TiO2 nanocrystallines can significantly improve the photocatalytic efficiency.

ALD TiO2 thin film as dielectric for Al/p-Si Schottky diode

Indian Academy of Sciences (India)

Abstract. Electrical analysis of Al/p-Si Schottky diode with titanium dioxide (TiO2) thin film was performed at ..... This work was partially supported by The Management Unit of Scientific Research Project of Bozok University and Hitit. University.

Growth and characterization of epitaxial anatase TiO2(001) on SrTiO3-buffered Si(001) using atomic layer deposition

International Nuclear Information System (INIS)

McDaniel, M.D.; Posadas, A.; Wang, T.; Demkov, A.A.; Ekerdt, J.G.

2012-01-01

Epitaxial anatase titanium dioxide (TiO 2 ) films have been grown by atomic layer deposition (ALD) on Si(001) substrates using a strontium titanate (STO) buffer layer grown by molecular beam epitaxy (MBE) to serve as a surface template. The growth of TiO 2 was achieved using titanium isopropoxide and water as the co-reactants at a substrate temperature of 225–250 °C. To preserve the quality of the MBE-grown STO, the samples were transferred in-situ from the MBE chamber to the ALD chamber. After ALD growth, the samples were annealed in-situ at 600 °C in vacuum (10 −7 Pa) for 1–2 h. Reflection high-energy electron diffraction was performed during the MBE growth of STO on Si(001), as well as after deposition of TiO 2 by ALD. The ALD films were shown to be highly ordered with the substrate. At least four unit cells of STO must be present to create a stable template on the Si(001) substrate for epitaxial anatase TiO 2 growth. X-ray diffraction revealed that the TiO 2 films were anatase with only the (004) reflection present at 2θ = 38.2°, indicating that the c-axis is slightly reduced from that of anatase powder (2θ = 37.9°). Anatase TiO 2 films up to 100 nm thick have been grown that remain highly ordered in the (001) direction on STO-buffered Si(001) substrates. - Highlights: ► Epitaxial anatase films are grown by atomic layer deposition (ALD) on Si(001). ► Four unit cells of SrTiO 3 on silicon create a stable template for ALD. ► TiO 2 thin films have a compressed c-axis and an expanded a-axis. ► Up to 100 nm thick TiO 2 films remain highly ordered in the (001) direction.

TiO2-BASED Composite Films for the Photodegradation of Oxytetracycline

Science.gov (United States)

Li, Hui; Guan, Ling-Xiao; Feng, Ji-Jun; Li, Fang; Yao, Ming-Ming

2015-02-01

The spread of the antibiotic oxytetracycline (OTC) has been thought as a threat to the safety of drinking water. In this paper, the photocatalytic activity of the nanocrystalline Fe/Ca co-doped TiO2-SiO2 composite film for the degradation of OTC was studied. The films were characterized by field emission scanning electron microscopy (FE-SEM) equipped with energy-dispersive spectroscopy (EDS), N2 adsorption/desorption isotherms, photoluminescence (PL) spectra, and UV-Vis diffraction reflectance absorption spectra (DRS). The FE-SEM results indicated that the Fe/Ca co-doped TiO2-SiO2 film was composed of smaller nanoparticles compared to pure TiO2 or TiO2-SiO2 film. The BET surface area results showed that the specific surface area of the pure TiO2, TiO2-SiO2 and Ca2+/Fe3+ co-doped TiO2-SiO2 is 118.3 m2g-1, 294.3 m2g-1 and 393.7 m2g-1, respectively. The DRS and PL spectra revealed that the Fe/Ca co-doped TiO2-SiO2 film had strong visible light adsorption and diminished electrons/holes recombination. Experimental results showed that the Fe/Ca co-doped TiO2-SiO2 film is effective in the degradation of OTC under both UV and visible light irradiation.

Effects of 6 MeV electron irradiation on the electrical properties and device parameters of Al/Al2O3/TiO2/n-Si MOS capacitors

International Nuclear Information System (INIS)

Laha, P.; Banerjee, I.; Barhai, P.K.; Das, A.K.; Bhoraskar, V.N.; Mahapatra, S.K.

2012-01-01

Highlights: ► The electron irradiation effects make variation in the device parameters. ► The device parameters changes due to percentage of defects and charge trapping. ► Leakage current of Al/Al 2 O 3 /TiO 2 /n-Si changes due to interface dangling bonds. ► The leakage current mechanism of MOS structures is due to Poole–Frenkel effect. - Abstract: The effects of 6 MeV electron irradiation on the electrical properties and device parameter characteristics of Al/Al 2 O 3 /TiO 2 /n-Si metal–oxide–semiconductor capacitors have been studied. Twelve Al/Al 2 O 3 /TiO 2 /n-Si MOS capacitors were fabricated using r.f. magnetron sputtering and divided into four groups. The first group was not irradiated and treated as virgin. The rest were irradiated with 6 MeV electrons at doses 10, 20, and 30 kGy, maintaining the dose rate at ∼1 kGy/min. Variations in crystallinity of the virgin and irradiated capacitors were studied using grazing incident X-ray diffraction. The thickness and in-depth elemental distributions of individual layers were determined using secondary ion mass apectrometry. Capacitance–voltage, conductance–voltage and leakage current–voltage characteristics of the virgin and irradiated samples were studied. The device parameters (flat band voltage, surface charge density and interface trap density of the virgin and irradiated structures) were determined. The electrical properties of the capacitors were investigated and the Poole–Frenkel coefficient of the capacitors was determined from leakage current measurements. The leakage current mechanism has been explained.

Multifunctional Roles of TiO 2 Nanoparticles for Architecture of Complex Core−Shells and Hollow Spheres of SiO 2 −TiO 2 −Polyaniline System

KAUST Repository

Wang, Dan Ping; Zeng, Hua Chun

2009-01-01

to prepare inorganic-polymer nanocomposites. In this work, we explore the roles of metal-oxide nanoparticles (anatase TiO2) in the area of constructional synthesis of highly complex core-shell and hollow sphere nanostructures comprising SiO2, TiO2

THE THERMODYNAMIC PROPERTIES OF MELTS OF DOUBLE SYSTEM MgO – Al2O3, MgO – SiO2, MgO – CaF2, Al2O3 – SiO2, Al2O3 – CaF2, SiO2 – CaF2

Directory of Open Access Journals (Sweden)

В. Судавцова

2012-04-01

Full Text Available Methodology of prognostication of thermodynamics properties of melts is presented from the coordinatesof liquidus of diagram of the state in area of equilibria a hard component is solution, on which energies ofmixing of Gibbs are expected in the double border systems of MgO – Al2O3, MgO – SiO2, MgO – CaF2,Al2O3 – SiO2, Al2O3 - CaF2, SiO2 - CaF2. For the areas of equilibrium there is quasibinary connection(MgAl2O4, Mg2SiO4, Al6Si2O13 – a grout at calculations was used equalization of Hauffe-Wagner. Theobtained data comport with literary

Preparation and characterization of TiO2 and Si-doped octacalcium phosphate composite coatings on zirconia ceramics (Y-TZP) for dental implant applications

Science.gov (United States)

Bao, Lei; Liu, Jingxiao; Shi, Fei; Jiang, Yanyan; Liu, Guishan

2014-01-01

In order to prevent the low temperature degradation and improve the bioactivity of zirconia ceramic implants, TiO2 and Si-doped octacalcium phosphate composite coating was prepared on zirconia substrate. The preventive effect on low temperature degradation and surface morphology of the TiO2 layer were studied. Meanwhile, the structure and property changes of the bioactive coating after doping Si were discussed. The results indicate that the dense TiO2 layer, in spite of some microcracks, inhibited the direct contact of the water vapor with the sample's surface and thus prevented the low temperature degradation of zirconia substrates. The acceleration aging test shows that the ratio of the monoclinic phase transition decreased from 10% for the original zirconia substrate to 4% for the TiO2-coated substrate. As to the Si-doped octacalcium phosphate coating prepared by biomimetic method, the main phase composition of the coating was octacalcium phosphate. The morphology of the coating was lamellar-like, and the surface was uniform and continuous with no cracks being observed. It is suggested that Si was added into the coating both through substituting for PO43- and doping as NaSiO3.

High performance GaN-based LEDs on patterned sapphire substrate with patterned composite SiO2/Al2O3 passivation layers and TiO2/Al2O3 DBR backside reflector.

Science.gov (United States)

Guo, Hao; Zhang, Xiong; Chen, Hongjun; Zhang, Peiyuan; Liu, Honggang; Chang, Hudong; Zhao, Wei; Liao, Qinghua; Cui, Yiping

2013-09-09

GaN-based light-emitting diodes (LEDs) on patterned sapphire substrate (PSS) with patterned composite SiO(2)/Al(2)O(3) passivation layers and TiO(2)/Al(2)O(3) distributed Bragg reflector (DBR) backside reflector have been proposed and fabricated. Highly passivated Al(2)O(3) layer deposited on indium tin oxide (ITO) layer with excellent uniformity and quality has been achieved with atomic layer deposition (ALD) technology. With a 60 mA current injection, an enhancement of 21.6%, 59.7%, and 63.4% in the light output power (LOP) at 460 nm wavelength was realized for the LED with the patterned composite SiO(2)/Al(2)O(3) passivation layers, the LED with the patterned composite SiO(2)/Al(2)O(3) passivation layers and Ag mirror + 3-pair TiO(2)/SiO(2) DBR backside reflector, and the LED with the patterned composite SiO(2)/Al(2)O(3) passivation layer and Ag mirror + 3-pair ALD-grown TiO(2)/Al(2)O(3) DBR backside reflector as compared with the conventional LED only with a single SiO(2) passivation layer, respectively.

Thermodynamic optimization of the (Na2O + SiO2 + NaF + SiF4) reciprocal system using the Modified Quasichemical Model in the Quadruplet Approximation

International Nuclear Information System (INIS)

Lambotte, Guillaume; Chartrand, Patrice

2011-01-01

Highlights: → We model the Na 2 O-SiO 2 -NaF-SiF 4 reciprocal system based on a comprehensive review of all available experimental data. → The assessment includes Na 2 O-SiO 2 and NaF-SiF 4 binary systems. → Improvements to the Modified Quasichemical Model in the Quadruplet Approximation are presented. → The very strong short-range ordering among first-nearest and second-nearest neighbors in this system is reproduced. → This work constitutes the first assessment for all compositions and temperatures of a reciprocal oxyfluoride system. - Abstract: All available thermodynamic and phase diagram data for the condensed phases of the ternary reciprocal system (NaF + SiF 4 + Na 2 O + SiO 2 ) have been critically assessed. Model parameters for the unary (SiF 4 ), the binary systems and the ternary reciprocal system have been found, which permit to reproduce the most reliable experimental data. The Modified Quasichemical Model in the Quadruplet Approximation was used for the oxyfluoride liquid solution, which exhibits strong first-nearest-neighbor and second-nearest-neighbor short-range ordering. This thermodynamic model takes into account both types of short-range ordering as well as the coupling between them. Model parameters have been estimated for the hypothetical high-temperature liquid SiF 4 .

[Effect of TiO2-SiO2-SnOx film with different firing temperatures on bond strength of low-fusing dental porcelain to pure titanium].

Science.gov (United States)

Zhang, Zichuan; Zhang, Pei

2015-07-01

To evaluate the influence of TiO(2)-SiO(2)-SnOx nano-coatings with different firing temperatures on the bond strength of low-fusing dental porcelain to pure titanium. The surface of pure titanium was coated uniformly with TiO(2)-SiO(2)-SnOx nano-coatings by solution-gelatin (Sol-Gel) technology and then fired at 300 °C (group A) or 750 °C (group B) for 1 h. The specimens without any coatings were the control group (group C). There were 10 specimens in each group. Dental porcelain was sintered on the surface of titanium specimens. Surface roughness and contact angle of the coatings were also detected. The titanium-porcelain bond strength was investigated according to YY 0621-2008 standards using three-point flexure bond test. The phase composition of the TiO(2)-SiO(2)-SnOx nano-coatings was characterized by X-ray diffraction(XRD). The interface of titanium-porcelain and TiO(2)-SiO(2)-SnOx nano-coatings were observed using scanning electron microscope (SEM). No rutile phase was found in these specimens of group A and group B. The surface roughness of group A, B, C was (0.97 ± 0.06), (0.99 ± 0.03), (0.96 ± 0.07) µm, respectively. No significant difference was found among the three groups. Compared with that of group C (64.37° ± 3.01°), contact angles detected in group A (52.04° ± 3.15°) and group B (85.27° ± 4.17°) were significantly different (P porcelain in group A [(35.66 ± 2.65) MPa] was significantly increased compared with those in group B [(26.18 ± 2.22) MPa] and group C [(31.66 ± 3.52) MPa]. SEM photomicrographs of titanium-porcelain interface morphology of the specimens before porcelain sintering showed that TiO(2)-SiO(2)-SnOx nano-coatings in group A were compact and homogeneous with petty cracks and those in group B was loose and arranged disorderly. TiO(2)-SiO(2)-SnOx nano-coating fired at 300 °C is significantly effective in improving the titanium-porcelain bond strength.

Two-dimensional TiO_2-based nanosheets co-modified by surface-enriched carbon dots and Gd_2O_3 nanoparticles for efficient visible-light-driven photocatalysis

International Nuclear Information System (INIS)

Lu, Dingze; Fang, Pengfei; Ding, Junqian; Yang, Minchen; Cao, Yufei; Zhou, Yawei; Peng, Kui; Kondamareddy, Kiran Kumar; Liu, Min

2017-01-01

Highlights: • Gd-C-TNSs with high stability and recycle usability were prepared by two-pot method. • Gd_2O_3 loading results in the structure changes of TNSs and increase of the Ti"3"+ ions. • Modified CDs leads to obvious increase of optical absorption ability and red shift. • Appropriate amount of Gd_2O_3 nanoparticles and CDs improve the separation of charges. • Gd-C-TNSs exhibit excellent synergistic photocatalytic activity for Cr(VI) and RhB. - Abstract: Two-dimensional TiO_2-based nanosheets (TNSs) co-modified by surface-enriched carbon dots (CDs) and Gd_2O_3 nanoparticles: (Gd-C-TNSs), capable of exhibiting visible-light-driven photo catalysis were synthesized using a two-pot hydrothermal route. The samples had a sheet-like structure, thickness of approximately 3.6 nm, large specific surface area of 240–350 cm"2/g. The CDs (2–3 nm) and Gd_2O_3 nanoparticles (1–2 nm) were highly dispersed over the surface of the nanosheets. The co-modification by Gd_2O_3 nanoparticles and CDs influenced the crystallinity, crystal structure, and surface area of the TNSs, and improved the visible-light absorption. Surface photocurrent and fluorescence spectral studies revealed that the photo-generated charge carrier separation efficiency could be improved by an appropriate amount of modification. A very high efficiency was obtained using 0.5 at% Gd/Ti and 3.0 g/L of CDs. The visible-light-induced photocatalytic activity is enhanced under the isolated Cr(VI) system, isolated Rhodamin B (RhB) system, and the synergism between RhB degradation and Cr(VI) reduction for the Gd-C-TNSs photocatalysts. Initially, the photocatalytic activity gradually increased with an increase in the amount of CDs, and then decreased after attaining a maximum, in the case where 0.5 at% Gd/Ti and 3.0 g/L of CDs were used. The enhancement in the photocatalytic activity was attributed to the synergetic effect of the Gd_2O_3 nanoparticles, TNSs, and CDs in the Gd-C-TNSs composites. The

A facile method to synthesize nitrogen and fluorine co-doped TiO2 nanoparticles by pyrolysis of (NH4)2TiF6

International Nuclear Information System (INIS)

Chen Daimei; Jiang Zhongyi; Geng Jiaqing; Zhu Juhong; Yang Dong

2009-01-01

The nitrogen and fluorine co-doped TiO 2 (N-F-TiO 2 ) nanoparticles of anatase crystalline structure were prepared by a facile method of (NH 4 ) 2 TiF 6 pyrolysis, and characterized by thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet visible (UV-Vis) spectroscopy etc. With the increase of calcination temperature, (NH 4 ) 2 TiF 6 decomposed into TiOF 2 and NH 4 TiOF 3 at first, and then formed anatase-type TiO 2 with thin sheet morphology. H 3 BO 3 as oxygen source can promote the formation of anatase TiO 2 , but decrease the F content in the N-F-TiO 2 materials due to the formation of volatile BF 3 during the precursor decomposition. The photocatalytic activity of the obtained N-F-TiO 2 samples was evaluated by the methylene blue degradation under visible light, and all the samples exhibited much higher photocatalytic activity than P25. Moreover, the merits and disadvantages of this proposed method to prepare doped TiO 2 are discussed.

Atomic structure of CaF2/MnF2-Si(1 1 1) superlattices from X-ray diffraction

International Nuclear Information System (INIS)

Alcock, Simon G.; Nicklin, C.L.; Howes, P.B.; Norris, C.A.; Kyutt, R.N.; Sokolov, N.S.; Yakovlev, N.L.

2007-01-01

X-ray reflectivity and non-specular crystal truncation rod scans have been used to determine the three-dimensional atomic structure of the buried CaF 2 -Si(1 1 1) interface and ultrathin films of MnF 2 and CaF 2 within a superlattice. We show that ultrathin films of MnF 2 , below a critical thickness of approximately four monolayers, are crystalline, pseudomorphic, and adopt the fluorite structure of CaF 2 . High temperature deposition of the CaF 2 buffer layer produces a fully reacted, CaF 2 -Si(1 1 1) type-B interface. The mature, 'long' interface is shown to consist of a partially occupied layer of CaF bonded to the Si substrate, followed by a distorted CaF layer. Our atomistic, semi-kinematical scattering method extends the slab reflectivity method by providing in-plane structural information

Aqueous suspensions of {alpha}Al{sub 2}O{sub 3}/SiC mixed systems

Energy Technology Data Exchange (ETDEWEB)

Pagnoux, C.; Baklouti, S.; Chartier, T.; Baumard, J.F. [ENSCI, Limoges (France). LMCTS

1997-12-31

The preparation of aqueous {alpha}-Al{sub 2}O{sub 3}, {alpha}-SiO{sub 2} and {alpha}-SiC suspensions with polyelectrolytes, respectively the NH{sub 4}{sup +} salt of polymethacrylic acid (PMA-NH{sub 4}{sup +}) and acidic form polyethylene imine (PEI-H{sup +}) is investigated. It is based on the adsorption of these polyelectrolytes which in turn depends mainly on the nature of the polyelectrolyte, and the charge density which develops on the powder surface in water. Good dispersion and stability of dispersions are then obtained through electrostatic and steric stabilization. As an application, the preparation of an Al{sub 2}O{sub 3}-SiC aqueous mixed slurry was investigated as a preliminary step for processing of Al{sub 2}O{sub 3}/SiC nanocomposites. (orig.) 2 refs.

Photocatalytic degradation of commercial phoxim over La-doped TiO2 nanoparticles in aqueous suspension.

Science.gov (United States)

Dai, Ke; Peng, Tianyou; Chen, Hao; Liu, Juan; Zan, Lin

2009-03-01

Photocatalytic degradation of commercial phoxim emulsion in aqueous suspension was investigated by using La-doped mesoporous TiO2 nanoparticles (m-TiO2) as the photocatalyst under UV irradiation. Effects of La-doping level, calcination temperature, and additional amount of the photocatalyst on the photocatalytic degradation efficiency were investigated in detail. Experimental results indicate that 20 mg L(-1) phoxim in 0.5 g L(-1) La/m-TiO2 suspension (the initial pH 4.43) can be decomposed as prolonging the irradiation time. Almost 100% phoxim was decomposed after 4 h irradiation according to the spectrophotometric analyses, whereas the mineralization rate of phoxim just reached ca. 80% as checked by ion chromatography (IC) analyses. The elimination of the organic solvent in the phoxim emulsion as well as the formation and decomposition of some degradation intermediates were observed by high-performance liquid chromatography-mass spectroscopy (HPLC-MS). On the basis of the analysis results on the photocatalytic degradation intermediates, two possible photocatalytic degradation pathways are proposed under the present experimental conditions, which reveal that both the hydrolysis and adsorption of phoxim under UV light irradiation play important roles during the photocatalytic degradation of phoxim.

Surface passivation of nano-textured fluorescent SiC by atomic layer deposited TiO2

DEFF Research Database (Denmark)

Lu, Weifang; Ou, Yiyu; Jokubavicius, Valdas

2016-01-01

Nano-textured surfaces have played a key role in optoelectronic materials to enhance the light extraction efficiency. In this work, morphology and optical properties of nano-textured SiC covered with atomic layer deposited (ALD) TiO2 were investigated. In order to obtain a high quality surface fo...

Study on photocatalytic degradation of methylene blue by H4SiW12O40/TiO2/beads%H4SiW12O40/TiO2/beads光催化降解亚甲基蓝的研究

Institute of Scientific and Technical Information of China (English)

黄卫红; 王晶博; 薛金娟; 闫永胜; 阮介兵

2009-01-01

以钛酸四丁酯为原料,空心微珠为载体,采用溶胶-凝胶法制备TiO2/beads光催化剂载体,然后浸渍法制备出H4SiW12O40/TiO2/beads表面负载修饰型复合光催化剂,并运用SEM、XRD、FT-IR和DRS对催化剂进行表征和分析.研究了H4SiW12O40/TiO2/beads对亚甲基蓝降解的光催化活性,考察了光强度、pH值、曝气量、底物浓度和催化剂用量等对催化效率的影响.实验结果表明,在中性条件下,H4SiW12O40/TiO2/beads催化剂的投加量为0.25 g/L,浓度为7.5 mg/L的亚甲基蓝溶液在250 W的紫外灯和600 W的可见光灯下光照60 min降解率分别可达到94.5%和55%.

Flexible free-standing TiO2/graphene/PVdF films as anode materials for lithium-ion batteries

International Nuclear Information System (INIS)

Ren, H.M.; Ding, Y.H.; Chang, F.H.; He, X.; Feng, J.Q.; Wang, C.F.; Jiang, Y.; Zhang, P.

2012-01-01

Highlights: ► Flexible TiO 2 /graphene electrode was prepared by a solvent evaporation technique. ► PVdF was used as substance to support the TiO 2 /graphene active materials. ► The flexible films can be employed as anode materials for Li-ion battery. - Abstract: Graphene composites were prepared by hydrothermal method using titanium dioxide (TiO 2 ) adsorbed graphene oxide (GO) sheets as precursors. Free-standing hybrid films for lithium-ion batteries were prepared by adding TiO 2 /graphene composites to the polyvinylidene fluoride (PVdF)/N-methyl-2-pyrrolidone (NMP) solution, followed by a solvent evaporation technique. These films were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), scanning electron microscopy (SEM) and various electrochemical techniques. Flexible films show an excellent cycling performance, which was attributed to the interconnected graphene conducting network, which depressed the increasing of electric resistance during the cycling.

Decolorization of dyeing wastewater in continuous photoreactors using tio2 coated glass tube media

Directory of Open Access Journals (Sweden)

Jutaporn Chanathaworn

2014-02-01

Full Text Available The present study deals with a decolorization development of malachite green (MG dyeing wastewater using TiO2 thin films coated glass tube media in photoreactor. The TiO2 photocatalyst was synthesized by three methods: TTIP sol-gel, TiO2 powder-modified sol, and TiO2 powder suspension coating on raschig ring glass tube media and was investigated crystallinity phase by SEM, XRD, and AFM. Degradation kinetics of the dyeing wastewater by photocatalytic was carried out under UV light irradiation. The Langmuir first-order model provided the best fit to the experimental data. The catalyst prepared by powder suspension technique and coated on glass tube had given the highest of decolorization kinetics and efficiency. Continuous photoreactor packed with the TiO2 coating media was designed and proven to be the high effectiveness for MG dyeing degradation and stable throughout the recyclability test. The light intensity, dye solution flow rate, and TiO2 loading were the most important parameters that response to decolorization efficiency. The optimum condition of photo decolorization of MG dye solution can be obtained from RSM model. Effectiveness of the synthesized TiO2 thin films using suspension technique and the continuous photoreactor design were obtained with a great potential to be proven for wastewater treatment at industrial scale.

Synergistic effect of N- and F-codoping on the structure and photocatalytic performance of TiO2.

Science.gov (United States)

Yu, Jiemei; Liu, Zongming; Zhang, Haitao; Huang, Taizhong; Han, Jitian; Zhang, Yihe; Chong, Daohuang

2015-02-01

Three types of TiO2 nanostructures were synthesized via a facile hydrolysis method at 195°C. Effects of the preparation method and doping with N and F on the crystal structure and photocatalytic performance of TiO2 were investigated. The nanomaterials were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller porosimetry, ultraviolet-visible diffuse reflectance spectroscopy and fluorescent emission spectra. Their photo-catalytic activity was examined by the photodegradation of methylene blue in aqueous solution under both ultra-violet and visible light irradiation. The results show that nitrogen and fluorine co-doped anatase TiO2 had the characteristics of a smaller crystalline size, broader light absorption spectrum and lower charge recombination than pure TiO2. Most importantly, more efficient photocatalytic activity under both ultra-violet and visible light was observed. The obtained N-F-TiO2 nanomaterial shows considerable potential for water treatment under sunlight irradiation. Copyright © 2014. Published by Elsevier B.V.

TiO2, SiO2 and ZrO2 Nanoparticles Synergistically Provoke Cellular Oxidative Damage in Freshwater Microalgae

Directory of Open Access Journals (Sweden)

Yinghan Liu

2018-02-01

Full Text Available Metal-based nanoparticles (NPs are the most widely used engineered nanomaterials. The individual toxicities of metal-based NPs have been plentifully studied. However, the mixture toxicity of multiple NP systems (n ≥ 3 remains much less understood. Herein, the toxicity of titanium dioxide (TiO2 nanoparticles (NPs, silicon dioxide (SiO2 NPs and zirconium dioxide (ZrO2 NPs to unicellular freshwater algae Scenedesmus obliquus was investigated individually and in binary and ternary combination. Results show that the ternary combination systems of TiO2, SiO2 and ZrO2 NPs at a mixture concentration of 1 mg/L significantly enhanced mitochondrial membrane potential and intracellular reactive oxygen species level in the algae. Moreover, the ternary NP systems remarkably increased the activity of the antioxidant defense enzymes superoxide dismutase and catalase, together with an increase in lipid peroxidation products and small molecule metabolites. Furthermore, the observation of superficial structures of S. obliquus revealed obvious oxidative damage induced by the ternary mixtures. Taken together, the ternary NP systems exerted more severe oxidative stress in the algae than the individual and the binary NP systems. Thus, our findings highlight the importance of the assessment of the synergistic toxicity of multi-nanomaterial systems.

Improved thermal conductivity of TiO2-SiO2 hybrid nanofluid in ethylene glycol and water mixture

Science.gov (United States)

Hamid, K. A.; Azmi, W. H.; Nabil, M. F.; Mamat, R.

2017-10-01

The need to study hybrid nanofluid properties such as thermal conductivity has increased recently in order to provide better understanding on nanofluid thermal properties and behaviour. Due to its ability to improve heat transfer compared to conventional heat transfer fluids, nanofluids as a new coolant fluid are widely investigated. This paper presents the thermal conductivity of TiO2-SiO2 nanoparticles dispersed in ethylene glycol (EG)-water. The TiO2-SiO2 hybrid nanofluids is measured for its thermal conductivity using KD2 Pro Thermal Properties Analyzer for concentration ranging from 0.5% to 3.0% and temperature of 30, 50 and 70°C. The results show that the increasing in concentration and temperature lead to enhancement in thermal conductivity at range of concentration studied. The maximum enhancement is found to be 22.1% at concentration 3.0% and temperature 70°C. A new equation is proposed based on the experiment data and found to be in good agreement where the average deviation (AD), standard deviation (SD) and maximum deviation (MD) are 1.67%, 1.66% and 5.13%, respectively.

Genotoxic and cytotoxic effects of ZnO nanoparticles for Dunaliella tertiolecta and comparison with SiO2 and TiO2 effects at population growth inhibition levels.

Science.gov (United States)

Schiavo, S; Oliviero, M; Miglietta, M; Rametta, G; Manzo, S

2016-04-15

The increasing use of oxide nanoparticles (NPs) in commercial products has intensified the potential release into the aquatic environment where algae represent the basis of the trophic chain. NP effects upon algae population growth were indeed already reported in literature, but the concurrent effects at cellular and genomic levels are still largely unexplored. Our work investigates the genotoxic (by COMET assay) and cytotoxic effects (by qualitative ROS production and cell viability) of ZnO nanoparticles toward marine microalgae Dunaliella tertiolecta. A comparison at defined population growth inhibition levels (i.e. 50% Effect Concentration, EC50, and No Observed Effect Concentration, NOEC) with SiO2 and TiO2 genotoxic effects and previously investigated cytotoxic effects (Manzo et al., 2015) was performed in order to elucidate the possible diverse mechanisms leading to algae growth inhibition. After 72h exposure, ZnO particles act firstly at the level of cell division inhibition (EC50: 2mg Zn/L) while the genotoxic action is evident only starting from 5mg Zn/L. This outcome could be ascribable mainly to the release of toxic ions from the aggregate of ZnO particle in the proximity of cell membrane. In the main, at EC50 and NOEC values for ZnO NPs showed the lowest cytotoxic and genotoxic effect with respect to TiO2 and SiO2. Based on Mutagenic Index (MI) the rank of toxicity is actually: TiO2>SiO2>ZnO with TiO2 and SiO2 that showed similar MI values at both NOEC and EC50 concentrations. The results presented herein suggest that up to TiO2 NOEC (7.5mg/L), the algae DNA repair mechanism is efficient and the DNA damage does not result in an evident algae population growth inhibition. A similar trend for SiO2, although at lower effect level with respect to TiO2, is observable. The comparison among all the tested nanomaterial toxicity patterns highlighted that the algae population growth inhibition occurred through pathways specific for each NP also related to their

Electronic states of SiO2-MxOy (MxOy=P205, TiO2 and ZrO2) glasses

Energy Technology Data Exchange (ETDEWEB)

Kowada, Y [Hyogo Univ. of Teacher Education, Hyogo (Japan); Adachi, H [Kyoto Univ. (Japan). Faculty of Engineering; Minami, T [Univ. of Osaka Prefecture, Osaka (Japan). Faculty of Engineering

1993-12-01

Using the sol-gel method the surface of metal and glass substrates can be modified. For example, stainless steel sheets coated with the SiO2-ZrO2 glass films have higher resistance to corrosion and oxidation. The coating films contain high concentration of alkali ions diffusing from the glass substrates. It suggests that the sodium ions are trapped strongly within the coating films and are blocked to further diffuse to the surface. This behavior must be associated with the chemical bonding around the sodium ions in the SiO2-TiO2 and SiO2-ZrO2 films. For better understanding of the chemical bonding in the glasses, the electronic states of the SiO2-MxOy glasses were calculated by means of the DV-Xa cluster method. In this paper, the calculation method is explained, the results are discussed and the conclusion is stated. 17 refs., 6 figs.

Enhanced solar light photodegradation of brilliant black bis-azo dye in aqueous solution by F, Sm3+ codoped TiO2

Science.gov (United States)

Mukonza, Sabastian S.; Nxumalo, Edward N.; Mamba, Bhekie B.; Mishra, Ajay K.

2017-05-01

This research focuses on improving the photocatalytic efficiency of TiO2 during the photo-mineralisation of brilliant black (BN) bis-azo dye pollutant in aqueous solution. This was achieved by improving the visible light activity of TiO2 photocatalyst semiconductor through co-doping of fluorine (F) and trivalent samarium ions (Sm3+) into a TiO2 matrix using a modified sol-gel synthesis method. Structural, morphological, and textural properties were evaluated using ultra-violet /visible spectroscopy (UV-visible), Raman spectroscopy, scanning electron microscopy coupled to energy dispersive X-ray spectroscopy (SEM/EDX) and X-ray diffraction spectroscopy (XRD). Photocatalytic and degradation efficiencies were assessed by decolourisation of BN dye in aqueous solution. Complete degradation of BN was attained after an irradiation time of 3 h using F, Sm3+-TiO2 (0.6% Sm3+) compared to 73.4% achieved using pristine TiO2. Pseudo first order kinetics rate constants (Ka) were 2.73×10-2 and 6.6×10-3 min-1 for Sm3+-TiO2 (0.6%Sm3+) and pristine TiO2, respectively, which translates to a remarkably high enhancement factor of 4. The results obtained established that doping of TiO2 by F and Sm3+ enhances the photocatalytic performance of TiO2 during solar light radiation which enables the utilisation of freely available and clean solar energy.

Photocatalytic degradation of mixed gaseous carbonyl compounds at low level on adsorptive TiO2/SiO2 photocatalyst using a fluidized bed reactor.

Science.gov (United States)

Zhang, Maolin; An, Taicheng; Fu, Jiamo; Sheng, Guoying; Wang, Xinming; Hu, Xiaohong; Ding, Xuejun

2006-06-01

An adsorptive silica-supported titania photocatalyst TiO(2)/SiO(2) was prepared by using nanosized titania (anatase) immobilized on silica gel by the sol-gel technique with the titanium tetra isopropoxide as the main raw material and acetic acid as the acid catalyst. Meanwhile the structure and properties of the TiO(2)/SiO(2) photocatalyst were studied by means of many modern analysis techniques such as TEM, XRD, and BET. Gas-solid heterogeneous photocatalytic decomposition of four carbonyl compounds mixture at low concentration levels over ultraviolet irradiated TiO(2)/SiO(2) photocatalyst were carried out with high degradation efficiencies in a coaxial triple-cylinder-type fluidized bed photocatalytic reactor, which provided efficient continuous contact of ultraviolet photons, silica-supported titania photocatalyst, and gaseous reactants. Experimental results showed that the photocatalyst had a high adsorption performance and a good photocatalytic activity for four carbonyl compounds mixture. Some factors influencing the photocatalytic decomposition of the mixed carbonyl compounds, i.e. the gas flowrate, relative humidity, concentration of oxygen, and illumination time, were discussed in detail. It is found that the photocatalytic reaction rate of four carbonyl compounds decreased in this order: propionaldehyde, acetone, acetaldehyde and formaldehyde.

Effects of TiO2 addition on microwave dielectric properties of Li2MgSiO4 ceramics

Science.gov (United States)

Rose, Aleena; Masin, B.; Sreemoolanadhan, H.; Ashok, K.; Vijayakumar, T.

2018-03-01

Silicates have been widely studied for substrate applications in microwave integrated circuits owing to their low dielectric constant and low tangent loss values. Li2MgSiO4 (LMS) ceramics are synthesized through solid-state reaction route using TiO2 as an additive to the pure ceramics. Variations in dielectric properties of LMS upon TiO2 addition in different weight percentages (0.5, 1.5, 2) are studied by keeping the sintering parameters constant. Crystalline structure, phase composition, and microstructure of LMS and LMS-TiO2 ceramics were studied using x-ray diffraction spectrometer and High Resolution Scanning electron microscope. Density was measured through Archimedes method and the microwave dielectric properties were examined by Cavity perturbation technique. LMS achieved relative permittivity (ε r) of 5.73 and dielectric loss (tan δ) of 5.897 × 10‑4 at 8 GHz. In LMS-TiO2 ceramics, 0.5 wt% TiO2 added LMS showed comparatively better dielectric properties than other weight percentages where ε r = 5.67, tan δ = 7.737 × 10‑4 at 8 GHz.

Photocatalytic degradation of clofibric acid, carbamazepine and iomeprol using conglomerated TiO2 and activated carbon in aqueous suspension.

Science.gov (United States)

Ziegmann, Markus; Frimmel, Fritz H

2010-01-01

The combination of powdered activated carbon (PAC) and TiO(2) has been tested for synergistic/antagonistic effects in the photocatalytic degradation of carbamazepine, clofibric acid and iomeprol. Synergistic effects are thought to be caused by rapid adsorption on the PAC surface followed by diffusion to the TiO(2) surface and photocatalytic degradation. The Freundlich constant K(F) was used for comparing the sorption properties of the three substances and it was found that K(F) for clofibric acid was 3 times lower than for carbamazepine and iomeprol, regardless of the kind of PAC used. A PAC with a distinct tendency to form conglomerates was selected so that a high percentage of the PAC surface was in direct proximity to the TiO(2) surface. The photocatalytic degradation of the pharmaceutically active compounds studied followed pseudo-first order kinetics. Synergistic effects only occurred for clofibric acid (factor 1.5) and an inverse relationship between adsorption affinity and synergistic effects was found. High affinity of the target substances to the PAC surface seemed to be counterproductive for the photocatalytic degradation.

Fe-N co-doped SiO2@TiO2 yolk-shell hollow nanospheres with enhanced visible light photocatalytic degradation

Science.gov (United States)

Wan, Hengcheng; Yao, Weitang; Zhu, Wenkun; Tang, Yi; Ge, Huilin; Shi, Xiaozhong; Duan, Tao

2018-06-01

SiO2@TiO2 yolk@shell hollow nanospheres (STNSs) is considered as an outstanding photocatalyst due to its tunable structure and composition. Based on this point, we present an unprecedentedly excellent photocatalytic property of STNSs toward tannic acid via a Fe-N co-doped strategy. Their morphologies, compositions, structure and properties are characterized. The Fe-N co-doped STNSs formed good hollow yolk@shell structure. The results show that the energy gap of the composites can be downgraded to 2.82 eV (pure TiO2 = 3.2 eV). Photocatalytic degradation of tannic acid (TA, 30 mg L-1) under visible light (380 nm TiO2 nanospheres, non-doped STNSs and N-doped STNSs, the Fe-N co-doped STNSs exhibits the highest activity, which can degrade 99.5% TA into CO2 and H2O in 80 min. The probable degradation mechanism of the composites is simultaneously proposed, the band gap of STNSs becomes narrow by co-doping Fe-N, so that the TiO2 shell can stimulate electrons under visible light exposure, generate the ions of radOH and radO2- with a strong oxidizing property. Therefore this approach works is much desired for radioactive organic wastewater photocatalytic degradation.

Synthesis And Characterization Of SiO2, SnO2 And TiO2 Metal Oxide Shells Covering Cu2O Particles

Directory of Open Access Journals (Sweden)

Yu Ri

2015-06-01

Full Text Available In this work is described a means of improving the chemical stability of Cu2O@SiO2, Cu2O@SnO2 and Cu2O@TiO2 materials. The SiO2, SnO2 and TiO2 coated samples were stable from pH 3 to pH 10 for up to seven days. To determine the stability of the coated nanoparticles, and their colloidal solutions under acidic and basic conditions, colloidal nanoparticle solutions with various pH values were prepared and monitored over time. Details of the effect of variations in pH on the phase stability of core-shell type Cu2O were characterized using transmission electron microscopy and X-ray diffraction.

Fabrication and characterization of 2.5D and 3D SiC{sub f}/SiC composites

Energy Technology Data Exchange (ETDEWEB)

Zhao, Shuang, E-mail: zhsh6007@126.co [Key Laboratory of Advanced Ceramic Fibers and Composites, National University of Defense Technology, Changsha 410073 (China); School of Mechanical, Aerospace, and Civil Engineering, University of Manchester, Manchester M13 9PL (United Kingdom); Zhou, Xingui; Yu, Jinshan [Key Laboratory of Advanced Ceramic Fibers and Composites, National University of Defense Technology, Changsha 410073 (China); Mummery, Paul [School of Mechanical, Aerospace, and Civil Engineering, University of Manchester, Manchester M13 9PL (United Kingdom)

2013-10-15

Highlights: • 2.5D and 3D KD-I SiC fiber fabrics were used as the reinforcement. • Closed porosity was investigated by X-ray tomographic techniques. • The properties of the composites were improved by the CVD process. -- Abstract: SiC{sub f}/SiC composites are considered promising candidate materials for fusion applications. 2.5D and 3D KD-I SiC fiber fabrics were used as the reinforcement and SiC{sub f}/SiC composites were fabricated via polymer impregnation and pyrolysis (PIP) process and coated with chemical vapor deposited (CVD) SiC. The porosity, thermal conductivity and mechanical property of the composites were characterized. The results indicated that 2.5D and 3D SiC{sub f}/SiC composites fabricated via PIP process exhibited high porosity, and hence low thermal conductivity. After the CVD process, the density, thermal conductivity and mechanical properties of the composites were increased.

TiO2 and SiC nanostructured films, organized CNT structures

Indian Academy of Sciences (India)

sized nanostructured TiO2 films through hydrolysis of titanium tetra-isopropoxide. (TTIP) [9 ... structured TiO2 as a photocatalyst is as follows [15]:. TiO2(ns) ... The deposited films were easily detached from the silica tube and subjected to. SEM.

Preparation of Porous F-WO3/TiO2 Films with Visible-Light Photocatalytic Activity by Microarc Oxidation

OpenAIRE

Yeh, Chung-Wei; Wu, Kee-Rong; Hung, Chung-Hsuang; Chang, Hao-Cheng; Hsu, Chuan-Jen

2012-01-01

Porous F-WO3/TiO2 (mTiO2) films are prepared on titanium sheet substrates using microarc oxidation (MAO) technique. The X-ray diffraction patterns show that visible-light (Vis) enabling mTiO2 films with a very high content of anatase TiO2 and high loading of WO3 are successfully synthesized at a low applied voltage of 300 V using electrolyte contenting NaF and Na2WO4 without subsequent heat treatment. The cross-sectional transmission electron microscopy micrograph reveals that the mTiO2 films...

TiO2 effect on crystallization mechanism and physical properties of nano glass-ceramics of MgO-Al2O3-SiO2 glass system.

Science.gov (United States)

Jo, Sinae; Kang, Seunggu

2013-05-01

The effect of TiO2 on the degree of crystallization, thermal properties and microstructure for MgO-Al2O3-SiO2 glass-ceramics system containing 0-13 wt% TiO2 and 0-1.5 wt% B2O3 in which the cordierite is the main phase was studied. Using Kissinger and Augis-Bennett equations, the activation energy, 510 kJ/mol and Avrami constant, 1.8 were calculated showing the surface-oriented crystallization would be preferred. The alpha-cordierite phase was generated in the glass-ceramics of containing TiO2 of 0-5.6 wt%. However, for the glass-ceramics of TiO2 content above 7 wt%, an alpha-cordierite disappeared and micro-cordierite phase was formed. The glass-ceramics of no TiO2 added had spherical crystals of few tens nanometer size spread in the matrix. As TiO2 content increased up to 5.6 wt%, a lump of dendrite was formed. In the glass-ceramics containing TiO2 7-13 wt%, in which the main phase is micro-cordierite, the dendrite crystal disappeared and a few hundred nanometer sized crystal particles hold tightly each other were generated. The thermal conductivity of glass-ceramics of both a-cordierite and micro-cordierite base decreased with TiO2 contend added. The thermal conductivity of glass-ceramics of 1.5 wt% TiO2 added was 3.4 W/mK which is 36% higher than that of glass-ceramics of no TiO2 added. The sintering temperature for 1.5 wt% TiO2 glass-ceramics was 965 degrees C which could be concluded as to apply to LTCC process for LED packaging.

Ultrafast switching in wetting properties of TiO2/YSZ/Si(001) epitaxial heterostructures induced by laser irradiation

International Nuclear Information System (INIS)

Bayati, M. R.; Molaei, R.; Narayan, J.; Joshi, S.; Narayan, R. J.

2013-01-01

We have demonstrated dark hydrophilicity of single crystalline rutile TiO 2 (100) thin films, in which rapid switching from a hydrophobic to a hydrophilic surface was achieved using nanosecond excimer laser irradiation. The TiO 2 /YSZ/Si(001) single crystalline heterostructures were grown by pulsed laser deposition and were subsequently irradiated by a single pulse of a KrF excimer laser at several energies. The wettability of water on the surfaces of the samples was evaluated. The samples were hydrophobic prior to laser annealing and turned hydrophilic after laser annealing. Superhydrophilic surfaces were obtained at higher laser energy densities (e.g., 0.32 J.cm −2 ). The stoichiometries of the surface regions of the samples before and after laser annealing were examined using XPS. The results revealed the formation of oxygen vacancies on the surface, which are surmised to be responsible for the observed superhydrophilic behavior. According to the AFM images, surface smoothening was greater in films that were annealed at higher laser energy densities. The samples exhibited hydrophobic behavior after being placed in ambient atmosphere. The origin of laser induced wetting behavior was qualitatively understood to stem from an increase of point defects near the surface, which lowered the film/water interfacial energy. This type of rapid hydrophobic/hydrophilic switching may be used to facilitate fabrication of electronic and photonic devices with novel properties.

TiO2 nanoparticle thin film deposition by matrix assisted pulsed laser evaporation for sensing applications

International Nuclear Information System (INIS)

Caricato, A.P.; Capone, S.; Ciccarella, G.; Martino, M.; Rella, R.; Romano, F.; Spadavecchia, J.; Taurino, A.; Tunno, T.; Valerini, D.

2007-01-01

The MAPLE technique has been used for the deposition of nanostructured titania (TiO 2 ) nanoparticles thin films to be used for gas sensors applications. An aqueous solution of TiO 2 nanoparticles, synthesised by a novel chemical route, was frozen at liquid nitrogen temperature and irradiated with a pulsed ArF excimer laser in a vacuum chamber. A uniform distribution of TiO 2 nanoparticles with an average size of about 10 nm was deposited on Si and interdigitated Al 2 O 3 substrates as demonstrated by high resolution scanning electron microscopy-field emission gun inspection (SEM-FEG). Energy dispersive X-ray (EDX) analysis revealed the presence of only the titanium and oxygen signals and FTIR (Fourier transform infra-red) revealed the TiO 2 characteristic composition and bond. A comparison with a spin coated thin film obtained from the same solution of TiO 2 nanoparticles is reported. The sensing properties of the films deposited on interdigitated substrates were investigated, too

Photocatalytic degradation of paracetamol on TiO2 nanoparticles and TiO2/cellulosic fiber under UV and sunlight irradiation

Directory of Open Access Journals (Sweden)

Nabil Jallouli

2017-05-01

Full Text Available In the present study, photocatalytic degradation of acetaminophen ((N-(4-hydroxyphe-nylacetamide, an analgesic drug has been investigated in a batch reactor using TiO2 P25 as a photocatalyst in slurry and under UV light. Using TiO2 P25 nanoparticles, much faster photodegradation of paracetamol and effective mineralization occurred, more than 90% of 2.65 × 10−4 M paracetamol was degraded under UV irradiation. Changes in pH values affected the adsorption and the photodegradation of paracetamol. pH 9.0 is found to be the optimum for the photodegradation of paracetamol. HPLC detected hydroquinone, benzoquinone, p-nitrophenol, and 1,2,4-trihydroxybenzene during the TiO2-assisted photodegradation of paracetamol among which some pathway products are disclosed for the first time. The results showed that TiO2 suspension/UV system is more efficient than the TiO2/cellulosic fiber mode combined to solar light for the photocatalytic degradation of paracetamol. Nerveless the immobilization of TiO2 showed many advantages over slurry system because it can enhance adsorption properties while allowing easy separation of the photocatalyst from the treated solution with improved reusable performance.

Synthesis of Si, N co-Doped Nano-Sized TiO2 with High Thermal Stability and Photocatalytic Activity by Mechanochemical Method

Directory of Open Access Journals (Sweden)

Peisan Wang

2018-05-01

Full Text Available Τhe photocatalytic activity in the range of visible light wavelengths and the thermal stability of the structure were significantly enhanced in Si, N co-doped nano-sized TiO2, and synthesized through high-energy mechanical milling of TiO2 and SiO2 powders, which was followed by calcination at 600 °C in an ammonia atmosphere. High-energy mechanical milling had a pronounced effect on the mixing and the reaction between the starting powders and greatly favored the transformation of the resultant powder mixture into an amorphous phase that contained a large number of evenly-dispersed nanocrystalline TiO2 particles as anatase seeds. The experimental results suggest that the elements were homogeneously dispersed at an atomic level in this amorphous phase. After calcination, most of the amorphous phase was crystallized, which resulted in a unique nano-sized crystalline-core/disordered-shell morphology. This novel experimental process is simple, template-free, and provides features of high reproducibility in large-scale industrial production.

Sol–gel hybrid membranes loaded with meso/macroporous SiO2, TiO2–P2O5 and SiO2–TiO2–P2O5 materials with high proton conductivity

International Nuclear Information System (INIS)

Castro, Yolanda; Mosa, Jadra; Aparicio, Mario; Pérez-Carrillo, Lourdes A.; Vílchez, Susana; Esquena, Jordi; Durán, Alicia

2015-01-01

In this work, highly conductive hybrid organic–inorganic membranes loaded with SiO 2 , TiO 2 –P 2 O 5 and SiO 2 –TiO 2 –P 2 O 5 meso/macroporous particles were prepared via a sol–gel process. Meso/macroporous particles were incorporated to hybrid membranes, for improving water retention and enhancing electrochemical performance. These particles with a polymodal pore size distribution were prepared by templating in highly concentrated emulsions, the particles showed a specific surface area between 50 m 2 /g (TiO 2 –P 2 O 5 ) and 300 m 2 /g (SiO 2 –TiO 2 –P 2 O 5 ). The particles were dispersed in a hybrid silica sol and further sprayed onto glass paper. The films were polymerized and sintered; those loaded with meso/macroporous particles had a homogenous distribution. High temperature proton conductivity measurements confirmed a high water retention. Conductivity of these materials is higher than that of Nafion ® at higher temperatures (120 °C) (2·10 −2  S/cm). This study provides processing guideline to achieve hybrid electrolytes for efficient conduction of protons due to their high surface area and porous structure. - Highlights: • Hybrid electrolyte with meso/macroporous particles were synthesized by sol–gel. • Depositions of hybrid solutions by spraying onto glass substrates were performed. • Proton conductivity was evaluated as a function of composition and porous structure

Surface characterization of poly(methylmethacrylate) based nanocomposite thin films containing Al2O3 and TiO2 nanoparticles

International Nuclear Information System (INIS)

Lewis, S.; Haynes, V.; Wheeler-Jones, R.; Sly, J.; Perks, R.M.; Piccirillo, L.

2010-01-01

Poly(methylmethacrylate) (PMMA) based nanocomposite electron beam resists have been demonstrated by spin coating techniques. When TiO 2 and Al 2 O 3 nanoparticles were directly dispersed into the PMMA polymer matrix, the resulting nanocomposites produced poor quality films with surface roughnesses of 322 and 402 nm respectively. To improve the surface of the resists, the oxide nanoparticles were encapsulated in toluene and methanol. Using the zeta potential parameter, it was found that the stabilities of the toluene/oxide nanoparticle suspensions were 7.7 mV and 19.4 mV respectively, meaning that the suspension was not stable. However, when the TiO 2 and Al 2 O 3 nanoparticles were encapsulated in methanol the zeta potential parameter was 31.9 mV and 39.2 mV respectively. Therefore, the nanoparticle suspension was stable. This method improved the surface roughness of PMMA based nanocomposite thin films by a factor of 6.6 and 6.4, when TiO 2 and Al 2 O 3 were suspended in methanol before being dispersed into the PMMA polymer.

Mo/Si multilayers with enhanced TiO II- and RuO II-capping layers

Science.gov (United States)

Yulin, Sergiy; Benoit, Nicolas; Feigl, Torsten; Kaiser, Norbert; Fang, Ming; Chandhok, Manish

2008-03-01

The lifetime of Mo/Si multilayer-coated projection optics is one of the outstanding issues on the road of commercialization of extreme-ultraviolet lithography (EUVL). The application of Mo/Si multilayer optics in EUVL requires both sufficient radiation stability and also the highest possible normal-incidence reflectivity. A serious problem of conventional high-reflective Mo/Si multilayers capped by silicon is the considerable degradation of reflective properties due to carbonization and oxidation of the silicon surface layer under exposure by EUV radiation. In this study, we focus on titanium dioxide (TiO II) and ruthenium dioxide (RuO II) as promising capping layer materials for EUVL multilayer coatings. The multilayer designs as well as the deposition parameters of the Mo/Si systems with different capping layers were optimized in terms of maximum peak reflectivity at the wavelength of 13.5 nm and longterm stability under high-intensive irradiation. Optimized TiO II-capped Mo/Si multilayer mirrors with an initial reflectivity of 67.0% presented a reflectivity drop of 0.6% after an irradiation dose of 760 J/mm2. The reflectivity drop was explained by the partial oxidation of the silicon sub-layer. No reflectivity loss after similar irradiation dose was found for RuO II-capped Mo/Si multilayer mirrors having initial peak reflectivity of 66%. In this paper we present data on improved reflectivity of interface-engineered TiO II- and RuO II-capped Mo/Si multilayer mirrors due to the minimization of both interdiffusion processes inside the multilayer stack and absorption loss in the oxide layer. Reflectivities of 68.5% at the wavelength of 13.4 nm were achieved for both TiO II- and RuO II-capped Mo/Si multilayer mirrors.

Single-crystal X-ray diffraction study of Cs2Er[Si6O14]F and Cs2Er[Si4O10]F

International Nuclear Information System (INIS)

Dabic, Predrag; Kremenovic, Aleksandar; Vulic, Predag; Kahlenberg, Volker; Schmidmair, Daniela

2016-01-01

Single-crystal growth experiments in the system CsF-Er 2 O 3 -SiO 2 resulted in the simultaneous crystallization of two chemically related compounds within the same run: Cs 2 Er[Si 6 O 14 ]F (phase I) and Cs 2 Er[Si 4 O 10 ]F (phase II). They represent the first examples for cesium erbium silicates containing fluorine. Basic crystallographic data are - phase I: space group Cmca, a=17.2556(6) Aa, b=24.6565(7) Aa, c=14.4735(5) Aa, V=6157.9(3) Aa 3 , Z=16; phase II: space group Pnma, a=22.3748(7) Aa, b=8.8390(2) Aa, c=11.9710(4) Aa, V=2367.5(1) Aa 3 , Z=8. The structures were determined by direct methods and refined to residuals of R(vertical stroke F vertical stroke)=0.0229 for 2920 (phase I) and 0.0231 for 2314 (phase II) independent observed reflections with I>2σ(I). The structure of phase I represents a previously unknown structure type with a three dimensional tetrahedral framework consisting of Q 3 and Q 4 groups in the ratio 2:1. Basic building units of the network are unbranched sechser single-chains running parallel to [001]. The network can be conveniently built up from the condensation of tetrahedral layers parallel to (010) or (100), respectively. The crystal structure of phase II can be classified as a tubular or columnar chain silicate indicating that the backbones of the structure are multiple chains of silicate tetrahedra. This structure is isotypic to a Cs 2 Y[Si 4 O 10 ]F, a compound that has been characterized previously. Alternatively, both compounds can be described as mixed octahedral-tetrahedral frameworks, which can be classified according to their polyhedral microensembles. A topological analysis of both nets is presented.

Glass-ceramic enamels derived from the Li2O-Na2O-Al2O3-TiO2-SiO2 system

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SNEZANA R. GRUJIC

2002-02-01

Full Text Available The results of research on the conditions for obtaining model glass-ceramic enamels, derived from the basic Li2O-Na2O-Al2O3-TiO2-SiO2 system, by varying the initial composition and thermal treatment conditions, are presented in this paper. Segregation of the crystal phases in the glassy-matrix was carried out during subsequent thermal treatment. The formation of different crystal phases was evidenced through the results of differential-thermal analysis and X-ray powder diffraction analysis.

Enhancement of visible-light photocatalytic activity of silver and mesoporous carbon co-modified Bi2WO6

International Nuclear Information System (INIS)

Zhao, Qian; Gong, Ming; Liu, Wangping; Mao, Yulin; Le, Shukun; Ju, Shang; Long, Fei; Liu, Xiufang; Liu, Kai; Jiang, Tingshun

2015-01-01

Graphical abstract: - Highlights: • Silver and mesoporous carbon co-modified Bi 2 WO 6 (Ag/Bi 2 WO 6 /CMK-3) composite was prepared. • Photocatalytic activity of Bi 2 WO 6 was remarkably enhanced by co-modification of silver and mesoporous carbon. • The degradation rate of MB can reach ca. 95.1% under visible light irradiation. • The Ag/Bi 2 WO 6 /CMK-3 composite has good stability and potential application prospects. - Abstract: Ordered mesoporous carbon CMK-3 was prepared by hard template method using SBA-15 as template, sucrose as carbon source. Flower/sphere-like Bi 2 WO 6 and CMK-3/Bi 2 WO 6 photocatalysts were synthesized by hydrothermal method, and then Ag/Bi 2 WO 6 and Ag/Bi 2 WO 6 /CMK-3 composite photocatalysts were prepared via a photoreduction process. The samples were characterized by XRD, UV–vis, TEM (HR-TEM), SEM, N 2 physical adsorption and PL and their photocatalytic activities were evaluated by the photocatalytic degradation of methylene blue (MB) under visible light irradiation. The results show that both incorporating of CMK-3 and Ag loading greatly improved the photocatalytic activity of Bi 2 WO 6 , and the content of CMK-3 and silver have an impact on the photocatalytic activity of Bi 2 WO 6 . The photocatalytic activity of Ag/Bi 2 WO 6 /CMK-3 photocatalyst is superior to the activities of CMK-3/Bi 2 WO 6 and Ag/Bi 2 WO 6 under comparable conditions, and Ag/Bi 2 WO 6 /CMK-3 photocatalyst has high stability and is easy to be recycled. Also, the mechanism for the enhancement of the photocatalytic activity of CMK-3 and Ag co-modified Bi 2 WO 6 was also investigated

TiO2/SiO2 prepared via facile sol-gel method as an ideal support for green synthesis of Ag nanoparticles using Oenothera biennis extract and their excellent catalytic performance in the reduction of 4-nitrophenol

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Bahar Khodadadi

2017-01-01

Full Text Available In the present study, the extract of the plant of Oenothera biennis was used to green synthesis of silver nanoparticles (Ag NPs as an environmentally friendly, simple and low cost method. And Additionally, TiO2/SiO2 was prepared via facile sol-gel method using starch as an important, naturally abundant organic polymer as an ideal support. The Ag NPs/TiO2/SiO2 as an effective catalyst was prepared through reduction of Ag+ ions using Oenothera biennis extract as the reducing and stabilizing agent and Ag NPs immobilization on TiO2/SiO2 surface in the absence of any stabilizer or surfactant. Several techniques such as FT-IR spectroscopy, UV-Vis spectroscopy, X-ray Diffraction (XRD, sScanning eElectron mMicroscopy (FE-SEM, Eenergy dDispersive X-ray sSpectroscopy (EDS, and Ttransmission Eelectron Mmicroscopy (TEM were used to characterize TiO2/SiO2, silver nanoparticles (Ag NPs, and Ag NPs/TiO2/SiO2. Moreover, the catalytic activity of the Ag NPs/ TiO2/SiO2 was investigated in the reduction of 4-nitrophenol (4-NP at room temperature. On the basis of the results, the Ag NPs/TiO2/SiO2 was found to be high catalytic activity highly active catalyst according to the experimental results in this study. In addition, Ag NPs/TiO2/SiO2 can be recovered and reused several times in the reduction of 4-NP with no significant loss of catalytic activity.

Evaluation method of TiO2-SiO2 ultra-low-expansion glasses with periodic striae using the LFB ultrasonic material characterization system.

Science.gov (United States)

Kushibiki, Jun-ichi; Arakawa, Mototaka; Ohashi, Yuji; Suzuki, Kouji

2006-09-01

Experimental procedures and standard specimens for characterizing and evaluating TiO2-SiO2 ultra-low expansion glasses with periodic striae using the line-focus-beam (LFB) ultrasonic material characterization system are discussed. Two types of specimens were prepared, with specimen surfaces parallel and perpendicular to the striae plane using two different grades of glass ingots. The inhomogeneities of each of the specimens were evaluated at 225 MHz. It was clarified that parallel specimens are useful for accurately measuring velocity variations of leaky surface acoustic waves (LSAWs) excited on a water-loaded specimen surface associated with the striae. Perpendicular specimens are useful for obtaining periodicities in the striae for LSAW propagation perpendicular to the striae plane on a surface and for precisely measuring averaged velocities for LSAW propagation parallel to the striae plane. The standard velocity of Rayleigh-type LSAWs traveling parallel to the striae plane for the perpendicular specimens was numerically calculated using the measured velocities of longitudinal and shear waves and density. Consequently, a reliable standard specimen with an LSAW velocity of 3308.18 +/- 0.35 m/s at 23 degrees C and its temperature coefficient of 0.39 (m/s)/degrees C was obtained for a TiO2-SiO2 glass with a TiO2 concentration of 7.09 wt%. A basis for the striae analysis using this ultrasonic method was established.

Structure of Na2O·MO·SiO2·CaF2 (M=Mg, Ca) oxyfluoride glasses

International Nuclear Information System (INIS)

Cheng Jinshu; Deng Wei; Wang Mitang

2012-01-01

(9-x)CaO·xMgO·15Na 2 O·60SiO 2 ·16CaF 2 (x=0, 2, 4, 6, and 9) oxyfluoride glasses were prepared. Utilizing the Raman scattering technique together with 29 Si and 19 F MAS NMR, the effect of alkaline metal oxides on the Q species of glass was characterized. Raman results show that as magnesia is added at the expense of calcium oxide, the disproportional reaction Q 3 →Q 4 +Q 2 (Q n is a SiO 4 tetrahedron with n bridging oxygens) prompted due to the high ionic field strength of magnesia, magnesium oxide entered into the silicate network as tetrahedral MgO 4 , and removed other modifying ions for charge compensation. This reaction was confirmed by 29 Si MAS NMR. 19 F MAS NMR results show that fluorine exists in the form of mixed calcium sodium fluoride species in all glasses and no Si-F bonds were formed. As CaO is gradually replaced by MgO (x=6, 9), a proportion of the magnesium ions combines with fluorine to form the MgF + species. Meanwhile, some part of Na + ions complex F - in the form of F-Na(6).

Silicon impurity release and surface transformation of TiO2 anatase and rutile nanoparticles in water environments

International Nuclear Information System (INIS)

Liu, Xuyang; Chen, Gexin; Erwin, Justin G.; Su, Chunming

2014-01-01

Surface transformation can affect the stability, reactivity, and toxicity of titanium dioxide (TiO 2 ) nanoparticles (NPs) in water environments. Herein, we investigated the release kinetics of Si impurity frequently introduced during NP synthesis and the resulting effect on TiO 2 NP transformation in aqueous solutions. The release of Si increased from 2 h to 19 d at three pHs with the order: pH 11.2 ≥ pH 2.4 > pH 8.2. The Si release process followed parabolic kinetics which is similar to diffusion controlled dissolution of minerals, and the release magnitude followed the order: 10 × 40 nm rutile > 50 nm anatase > 30 × 40 nm rutile. FTIR data indicated preferential dissolving of less polymerized Si species on NP surface. Surface potential and particle size of TiO 2 NPs remained almost constant during the 42-day monitoring, implying the unaffected stability and transport of these NPs by the incongruent dissolution of impurities. Highlights: • Si impurity may affect the colloid stability, reactivity, and toxicity of TiO 2 NPs. • Si impurity gradually released during 2 h – 19 d following a parabolic curve. • FTIR data indicated less polymerized Si species dissolved from TiO 2 NPs. • Surface potential and size of TiO 2 remained constant during impurity release. • NP production needs to consider ion release and environmental transformation. -- The incongruent dissolution of surface charge determining Si impurity did not significantly affect the surface potential and aggregation status of TiO 2 nanoparticles in aqueous solutions

Investigation of anodic TiO2 nanotube composition with high spatial resolution AES and ToF SIMS

Science.gov (United States)

Dronov, Alexey; Gavrilin, Ilya; Kirilenko, Elena; Dronova, Daria; Gavrilov, Sergey

2018-03-01

High resolution Scanning Auger Electron Spectroscopy (AES) and Time-of-Flight Secondary Ion Mass-Spectrometry (ToF SIMS) were used to investigate structure and elemental composition variation of both across an array of TiO2 nanotubes (NTs) and single tube of an array. The TiO2 NT array was grown by anodic oxidation of Ti foil in fluorine-containing ethylene glycol electrolyte. It was found that the studied anodic TiO2 nanotubes have a layered structure with rather sharp interfaces. The differences in AES depth profiling results of a single tube with the focused primary electron beam (point analysis) and over an area of 75 μm in diameter of a nanotube array with the defocused primary electron beam are discussed. Depth profiling by ToF SIMS was carried out over approximately the same size of a nanotube array to determine possible ionic fragments in the structure. The analysis results show that the combination of both mentioned methods is useful for a detailed analysis of nanostructures with complex morphology and multi-layered nature.

Preparation of flexible TiO2 photoelectrodes for dye-sensitized solar cells

Science.gov (United States)

Li, Wen-Ren; Wang, Hsiu-Hsuan; Lin, Chia-Feng; Su, Chaochin

2014-09-01

Dye-sensitized solar cells (DSSCs) based on nanocrystalline TiO2 photoelectrodes on indium tin oxide (ITO) coated polymer substrates have drawn great attention due to its lightweight, flexibility and advantages in commercial applications. However, the thermal instability of polymer substrates limits the process temperature to below 150 °C. In order to assure high and firm interparticle connection between TiO2 nanocrystals (TiO2-NC) and polymer substrates, the post-treatment of flexible TiO2 photoelectrodes (F-TiO2-PE) by mechanical compression was employed. In this work, Degussa P25 TiO2-NC was mixed with tert-butyl alcohol and DI-water to form TiO2 paste. F-TiO2-PE was then prepared by coating the TiO2 paste onto ITO coated polyethylene terephthalate (PET) substrate using doctor blade followed by low temperature sintering at 120 °C for 2 hours. To study the effect of mechanical compression, we applied 50 and 100 kg/cm2 pressure on TiO2/PET to complete the fabrication of F-TiO2-PE. The surface morphology of F-TiO2-PE was characterized using scanning electron microscopy. The resultant F-TiO2-PE sample exhibited a smooth, crack-free structure indicating the great improvement in the interparticle connection of TiO2-NC. Increase of compression pressure could lead to the increase of DSSC photoconversion efficiency. The best photoconversion efficiency of 4.19 % (open circuit voltage (Voc) = 0.79 V, short-circuit photocurrent density (Jsc) = 7.75 mA/cm2, fill factor (FF) = 0.68) was obtained for the F-TiO2-PE device, which showed great enhancement compared with the F-TiO2-PE cell without compression treatment. The effect of compression in DSSC performance was vindicated by the electrochemical impedance spectroscopy measurement.

Efficient catalytic ozonation by ruthenium nanoparticles supported on SiO2 or TiO2: Towards the use of a non-woven fiber paper as original support

KAUST Repository

Biard, Pierre-François

2015-12-24

This work focuses on the use of Ru(0) nanoparticles as heterogeneous catalyst for ozone decomposition and radical production. In a first set of experiments, the nanoparticles have been deposited on two inorganic supports (TiO2 or SiO2) by a wet impregnation approach. This study confirmed the high potential of Ru nanoparticles as active species for ozone decomposition at pH 3, since the ozone half-life time decreases by a factor 20-25, compared to the reference experiment carried out without any catalyst. The enhancement of the ozone decomposition kinetics provided an improved radical production and a higher transient radical concentration in a shorten ozone exposure. Consequently, lower oxidant dosage and contact time would be necessary. Thus, very significant atrazine consumption kinetics enhancements were measured. In a second set of experiments, a non-woven fiber paper composed of a TiO2/SiO2/zeolite mixture has been evaluated as an original support for ruthenium nanoparticles. Even if lower ozone decomposition kinetics was observed compared to TiO2 or SiO2, this support would be a promising alternative to inorganic powders to avoid the catalyst recovery step and to design reactors such as tubular reactors. A new numerical procedure is presented for the evaluation of the transient HO° concentration and of the Rct.

Enhanced photoelectrochemical properties of F-containing TiO2 sphere thin film induced by its novel hierarchical structure

International Nuclear Information System (INIS)

Dong Xiang; Tao Jie; Li Yingying; Zhu Hong

2009-01-01

The novel nanostructured F-containing TiO 2 (F-TiO 2 ) sphere was directly synthesized on the surface of Ti foil in the solution of NH 4 F and HCl by one-step hydrothermal approach under low-temperature condition. The samples were characterized respectively by means of field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results showed that the F-TiO 2 sphere was hierarchical structure, which composed of porous octahedron crystals with one truncated cone, leading to a football-like morphology. XPS results indicated that F - anions were just physically adsorbed on the surface of TiO 2 microspheres. The studies on the optical properties of the F-TiO 2 were carried out by UV-vis light absorption spectrum. The surface fluorination of the spheres, the unique nanostructure induced accessible macropores or mesopores, and the increased light-harvesting abilities were crucial for the high photoelectrochemical activity of the synthesized F-TiO 2 sphere for water-splitting. The photocurrent density of the F-TiO 2 sphere thin film was more than two times than that of the P25 thin film. Meanwhile, a formation mechanism was briefly proposed. This approach could provide a facile method to synthesize F-TiO 2 microsphere with a special morphology and hierarchical structure in large scale.

PREPARATION AND CHARACTERIZATION OF TiO2-ZEOLITE AND ITS APPLICATION TO DEGRADE TEXTILLE WASTEWATER BY PHOTOCATALYTIC METHOD

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Yeslia Utubira

2010-06-01

Full Text Available The preparation of titanium oxide-zeolite composite (TiO2-zeolite has been done. Preparation was initiated by dispersing oligocation of titanium solution into suspension of natural zeolite. The suspension was stirred and then filtered to separate the solid phase from the filtrate. The solid phase was heated by microwave oven to convert the oligocations into its oxide forms and the resulting material (called as TiO2-zeolite then was used to photodegrade the wastewater of PT.Jogjatex The TiO2-zeolite and unmodified zeolite were characterized using X-ray diffractometry, FT-IR spectro-photometry, X-ray fluorescence (XRF and gas sorption analysis (GSA methods to determine their physicochemical properties. Photocatalytic activity of TiO2-Zeolite was tested by exposing the suspension of TiO2-Zeolite/wastewater by the UV light of 366 nm at room temperature for 15 - 75 minutes. Characterization results exhibited that the formation of TiO2 on internal as well as external surfaces of Zeolite could not be detected  with X-ray diffractometry as well as  FT-IR spectrophotometry, however elemental analysis result with XRF indicated that titanium concentration in zeolite increased due to the inclusion, i.e from 0.26% (w/w in zeolite to 2.80% (w/w in TiO2-zeolite. Characterization result by GSA exhibited the increased of specific surface area from 19.57 m2/g in zeolite to 67.96 m2/g in TiO2-zeolite; total pore volume from 20.64 x 10-3 mL/g in zeolite to 49.561 x 10-3 mL/g in TiO2-Zeolite; pore radius average decreased from 21.10 Å in zeolite to 14.58 Å in TiO2-zeolite. Photocatalytic activity test of TiO2-zeolite on wastewater of PT. Jogjatex showed that UV radiation for 75 minutes on the mixture of TiO2-zeolite and wastewater resulted in the decreased of  COD number up to 57.85%. Meanwhile the sorption study showed that zeolite and TiO2-zeolite could decrease COD number of wastewater up to 43.95% and 57.85%, respectively.   Keywords: TiO2-zeolite

Stability of titania nanoparticles in soil suspensions and transport in saturated homogeneous soil columns

International Nuclear Information System (INIS)

Fang Jing; Shan Xiaoquan; Wen Bei; Lin Jinming; Owens, Gary

2009-01-01

The stability of TiO 2 nanoparticles in soil suspensions and their transport behavior through saturated homogeneous soil columns were studied. The results showed that TiO 2 could remain suspended in soil suspensions even after settling for 10 days. The suspended TiO 2 contents in soil suspensions after 24 h were positively correlated with the dissolved organic carbon and clay content of the soils, but were negatively correlated with ionic strength, pH and zeta potential. In soils containing soil particles of relatively large diameters and lower solution ionic strengths, a significant portion of the TiO 2 (18.8-83.0%) readily passed through the soils columns, while TiO 2 was significantly retained by soils with higher clay contents and salinity. TiO 2 aggregate sizes in the column outflow significantly increased after passing through the soil columns. The estimated transport distances of TiO 2 in some soils ranged from 41.3 to 370 cm, indicating potential environmental risk of TiO 2 nanoparticles to deep soil layers. - TiO 2 nanoparticles could efficiently suspend in soil suspensions and potentially transport to deeper soil layers

Reaction of silanes in supercritical CO2 with TiO2 and Al2O3.

Science.gov (United States)

Gu, Wei; Tripp, Carl P

2006-06-20

Infrared spectroscopy was used to investigate the reaction of silanes with TiO2 and Al2O3 using supercritical CO2 (Sc-CO2) as a solvent. It was found that contact of Sc-CO2 with TiO2 leads to partial removal of the water layer and to the formation of carbonate, bicarbonate, and carboxylate species on the surface. Although these carbonate species are weakly bound to the TiO2 surface and can be removed by a N2 purge, they poison the surface, resulting in a lower level of reaction of silanes with TiO2. Specifically, the amount of hexamethyldisilazane adsorbed on TiO2 is about 10% of the value obtained when the reaction is performed from the gas phase. This is not unique to TiO2, as the formation of carbonate species also occurs upon contact of Al2O3 with Sc-CO2 and this leads to a lower level of reaction with hexamethyldisilazane. This is in contrast to reactions of silanes on SiO2 where Sc-CO2 has several advantages over conventional gaseous or nonaqueous methods. As a result, caution needs to be applied when using Sc-CO2 as a solvent for silanization reactions on oxides other than SiO2.

Preparation of Porous F-WO3/TiO2 Films with Visible-Light Photocatalytic Activity by Microarc Oxidation

Directory of Open Access Journals (Sweden)

Chung-Wei Yeh

2012-01-01

Full Text Available Porous F-WO3/TiO2 (mTiO2 films are prepared on titanium sheet substrates using microarc oxidation (MAO technique. The X-ray diffraction patterns show that visible-light (Vis enabling mTiO2 films with a very high content of anatase TiO2 and high loading of WO3 are successfully synthesized at a low applied voltage of 300 V using electrolyte contenting NaF and Na2WO4 without subsequent heat treatment. The cross-sectional transmission electron microscopy micrograph reveals that the mTiO2 films feature porous networks connected by many micron pores. The diffused reflection spectrum displays broad absorbance across the UV-Vis regions and a significant red shift in the band gap energy (∼2.23 eV for the mTiO2 film. Owing to the high specific surface area from the porous microstructure, the mTiO2 film shows a 61% and 50% rate increase in the photocatalytic dye degradation, as compared with the N,C-codoped TiO2 films under UV and Vis irradiation, respectively.

TiO2/Pt/TiO2 Sandwich Nanostructures: Towards Alcohol Sensing and UV Irradiation-Assisted Recovery

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Rungroj Maolanon

2017-01-01

Full Text Available The TiO2/Pt/TiO2 sandwich nanostructures were synthesized by RF magnetron sputtering and demonstrated as an alcohol sensor at room-temperature operation with a fast recovery by UV irradiation. The TiO2/Pt/TiO2 layers on SiO2/Si substrate were confirmed by Auger electron spectroscopy with the interdiffusion of each layer. The TiO2/Pt/TiO2 layers on printed circuit board show the superior sensor response to alcohol in terms of the sensitivity and stability compared to the nonsandwich structure, that is, the only Pt layer or the TiO2/Pt structures. Moreover, the recovery time of the TiO2/Pt/TiO2 was improved by UV irradiation-assisted recovery. The optimum TiO2/Pt/TiO2 with thicknesses of the undermost TiO2 layer, a Pt layer, and the topmost TiO2 layer being 50 nm, 6 nm, and 5 nm, respectively, showed the highest response to ethanol down to 10 ppm. Additionally, TiO2/Pt/TiO2 shows an excellent sensing stability and exhibits different sensing selectivity among ethanol, methanol, and 2-propanol. The sensing mechanism could be attributed to the change of Pt work function during vapor adsorption. The TiO2 layer plays an important role in UV-assisted recovery by photocatalytic activity and the topmost TiO2 acts as protective layer for Pt.

VO2/TiO2 Nanosponges as Binder-Free Electrodes for High-Performance Supercapacitors

Science.gov (United States)

Hu, Chenchen; Xu, Henghui; Liu, Xiaoxiao; Zou, Feng; Qie, Long; Huang, Yunhui; Hu, Xianluo

2015-11-01

VO2/TiO2 nanosponges with easily tailored nanoarchitectures and composition were synthesized by electrostatic spray deposition as binder-free electrodes for supercapacitors. Benefiting from the unique interconnected pore network of the VO2/TiO2 electrodes and the synergistic effect of high-capacity VO2 and stable TiO2, the as-formed binder-free VO2/TiO2 electrode exhibits a high capacity of 86.2 mF cm-2 (~548 F g-1) and satisfactory cyclability with 84.3% retention after 1000 cycles. This work offers an effective and facile strategy for fabricating additive-free composites as high-performance electrodes for supercapacitors.

VO2/TiO2 Nanosponges as Binder-Free Electrodes for High-Performance Supercapacitors.

Science.gov (United States)

Hu, Chenchen; Xu, Henghui; Liu, Xiaoxiao; Zou, Feng; Qie, Long; Huang, Yunhui; Hu, Xianluo

2015-11-04

VO2/TiO2 nanosponges with easily tailored nanoarchitectures and composition were synthesized by electrostatic spray deposition as binder-free electrodes for supercapacitors. Benefiting from the unique interconnected pore network of the VO2/TiO2 electrodes and the synergistic effect of high-capacity VO2 and stable TiO2, the as-formed binder-free VO2/TiO2 electrode exhibits a high capacity of 86.2 mF cm(-2) (~548 F g(-1)) and satisfactory cyclability with 84.3% retention after 1000 cycles. This work offers an effective and facile strategy for fabricating additive-free composites as high-performance electrodes for supercapacitors.

Photon stimulated desorption investigations of positive ions of MgO, TiO2, Yb2O3, Nd2O3, H2O/Si(100), CaF2/Si and of H2O, CO and NO on Yb and Nd in the energy range 14 eV up to 800 eV

International Nuclear Information System (INIS)

Senf, F.

1987-01-01

Photon-stimulated desorption of positive ions from surfaces has been studied with synchrotron radiation in the photon energy range 14 -800 eV of the 'FLIPPER'-monochromator using a time-of-flight mass spectrometer. TiO 2 , as a prototype of a maximal valency ionic compound, shows a strong desorption of O +- in the photon energy range of the Ti 3 p → 3d- and Ti 2p → 3d-resonance as well as at the 0 1s-excitation due to intraatomic respectively intraatomic Auger decays, which is in agreement with the Knotek-Feibelman model. The desorption of F + from CaF 2 -covered silicon is found to follow the respective excitation and decay processes in Ca and F. In addition, the very large cross section for the F + desorption causes a radiation damage by photons of more than about 30 eV. The adsorbate system H 2 O/Si (100) needs a multiple electron excitation to show a significant desorption setting in only 30 eV above the 0 1s threshold. The rare earth metals Yb and Nd covered with O 2 , H 2 O, CO or NO exhibit a competitive desorption of O + partly due to intraatomic Auger decays caused by single electron excitations and partly due to multiple electron excitations. The variation of the 0 + yield with regard to the different adsorbates on Yb and Nd is unexpectedly low. A detailed investigation was concerned with thin oxidized Mg-films and differently prepared MgO-single-crystals. Here we found a very efficient desorption of O + and H + resulting from the excitation of O 1s-surface-excitons. In addition, the strong hole-hole-interaction energy of crystalline MgO appears to be responsible for a suppressed O + -signal in the energy range of the Mg 2p-excitation. (orig./BHO)

Manufacturing and investigation of surface morphology and optical properties of composite thin films reinforced by TiO2, Bi2O3 and SiO2 nanoparticles

Science.gov (United States)

Jarka, Paweł; Tański, Tomasz; Matysiak, Wiktor; Krzemiński, Łukasz; Hajduk, Barbara; Bilewicz, Marcin

2017-12-01

The aim of submitted paper is to present influence of manufacturing parameters on optical properties and surface morphology of composite materials with a polymer matrix reinforced by TiO2 and SiO2 and Bi2O3 nanoparticles. The novelty proposed by the authors is the use of TiO2 and SiO2 and Bi2O3 nanoparticles simultaneously in polymeric matrix. This allows using the combined effect of nanoparticles to a result composite material. The thin films of composite material were prepared by using spin-coating method with various spinning rates from solutions of different concentration of nanoparticles. In order to prepare the spinning solution polymer, Poly(methyl methacrylate) (PMMA) was used as a matrix. The reinforcing phase was the mixture of the nanoparticles of SiO2, TiO2 and B2O3. In order to identify the surface morphology of using thin films and arrangement of the reinforcing phase Atomic Force Microscope (AFM) and Scanning Electron Microscope (SEM) were used. In order to study the optical properties of the obtained thin films, the thin films of composites was subjected to an ellipsometry analysis. The measurements of absorbance of the obtained materials, from which the value of the band gap width was specified, were carried out using the UV/VIS spectroscopy. The optical properties of obtain composite thin films depend not only on the individual components used, but also on the morphology and the interfacial characteristics. Controlling the participation of three kinds of nanoparticles of different sizes and optical parameters allows to obtaining the most optimal optical properties of nanocomposites and also controlling the deposition parameters allows to obtaining the most optimal surface morphology of nanocomposites.

New TiO2/DSAT Immobilization System for Photodegradation of Anionic and Cationic Dyes

Directory of Open Access Journals (Sweden)

Wan Izhan Nawawi Wan Ismail

2015-01-01

Full Text Available A new immobilized TiO2 technique was prepared by coating TiO2 solution onto double-sided adhesive tape (DSAT as a thin layer binder without adding any organic additives. Glass plate was used as support material to immobilized TiO2/DSAT. Two different charges of dyes were applied, namely, anionic reactive red 4 (RR4 and cationic methylene blue (MB dyes. Photocatalytic degradation of RR4 and MB dyes was observed under immobilized TiO2/DSAT with the degradation rate slightly lower and higher, respectively, compared with TiO2 in suspension mode. It was observed that DSAT is able to provide a very strong intact between glass and TiO2 layers thus making the reusability of immobilized TiO2/DSAT be up to 30 cycles. In fact, a better photodegradation activity was observed by number of cycles due to increasing formation of pores on TiO2 surface observed by SEM analysis.

Influence of ionic strength in the adsorption and during photocatalysis of reactive black 5 azo dye on TiO2 coated on non woven paper with SiO2 as a binder

International Nuclear Information System (INIS)

Aguedach, Abdelkahhar; Brosillon, Stephan; Morvan, Jean; Lhadi, El Kbir

2008-01-01

Reactive black 5 (RB5), an azo dye, was degraded by using UV-irradiated TiO 2 coated on non woven paper with SiO 2 as a binder. The adsorption capacity of the photocatalyst was studied at natural pH, superior to pH pzc of the binder, for various ionic strengths. Different salts such as NaCl, KCl, CaCl 2 , LiCl, Ca(NO 3 ) 2 were used to increase the ionic strength. The presence of salt increased the adsorption capacity. The electrostatic interactions between dye and oxide surface charges (TiO 2 /SiO 2 ) is very important in the adsorption phenomena. The effect of the ionic strength of the solution on photocatalyst degradation was studied. The rate of degradation was increased by the presence of salts in the range of the experimental conditions. The increase of the initial decolorization rate was observed in the following order: Ca 2+ > K + > Na + > Li + . Experiments with different anions (Cl - , NO 3 - ) had shown that nitrate was an indifferent electrolyte for the adsorption and photodegradation of the dye on SiO 2 /TiO 2

Evaluation of micro-abrasion-corrosion on SiO2-TiO2-ZrO2 coatings synthesized by the sol-gel method

Science.gov (United States)

Bautista Ruiz, J.; Aperador, W.; Caballero Gómez, J.

2016-02-01

The medical science and the engineering, work to improve the materials used in the manufacture of joint implants, since they have a direct impact on the quality of people life. The surgical interventions are increasing worldwide with a high probability of a second or even a third intervention. Around these circumstances, it was evaluated the behaviour against microabrasion-corrosion phenomena on SiO2 TiO2 ZrO2 coatings, synthesized by the sol-gel method with concentration of the Si/Ti/Zr precursors: 10/70/20 and 10/20/70. The coatings were deposited on AISI 316 LVM stainless steel substrates. The morphological characterization of the wear was made by AFM techniques. It was observed that the coatings with higher levels of titanium have a good response to the phenomena of microabrasion-corrosion.

Passivation of surface-nanostructured f-SiC and porous SiC

DEFF Research Database (Denmark)

Ou, Haiyan; Lu, Weifang; Ou, Yiyu

The further enhancement of photoluminescence from nanostructured fluorescent silicon carbide (f-SiC) and porous SiC by using atomic layer deposited (ALD) Al2O3 is studied in this paper.......The further enhancement of photoluminescence from nanostructured fluorescent silicon carbide (f-SiC) and porous SiC by using atomic layer deposited (ALD) Al2O3 is studied in this paper....

A.C. impedance, XRD, DSC, SEM and charge/discharge studies on Al2O3, TiO2, SiO2 dispersoid LiPF6/PVC/PVdF-co-HFP composite polymer electrolytes by phase inversion

Science.gov (United States)

Vickraman, P.; Gopukumar, S.

2017-07-01

The PVC/PVdF-co-HFP composite polymer electrolyte membranes (CPEMs) by varying blend ratios 1:1, 1:2, and 2:1 with fixed content of Al2O3, TiO2 and SiO2 having soaked in 0.5 M LiPF6 in EC/DEC (1:1) v/v) have been prepared by phase inversion. CPEMs of higher ionic conductivity (not dependent on electrolyte uptake as observed in our study) ASA4 (3.61×10-4 Scm-1), TSA3 (1.53×10-4 Scm-1), and SSA3 (4.81×10-4 Scm-1) have been only chosen for XRD, DSC, SEM and electrochemical studies. In XRD, crystalline peaks (phases) of PVdF have been noted with/without change in intensity as well as FWHM which correspond to type of filler interaction with host matrix. In DSC, it is observed that shifts in baseline, melting endotherms, and area under the endotherms indicating the thermal hist ory of PVC (Tg = 82 ° C) and melting of VdF crystallites varied with nature of the filler dispersoid. In SEM, the coagulated fibrils of the polymer coiled with the sponge like structure has been mapped. The charge/discharge studies are carried out on these CPEMs at C/10 rate in the voltage range 2.8 V - 4.2 V, and it is noted that the TSA3 showed better cycling performance with good capacity retention i.e., 50 cycles with 66% capacity retention than ASA4 of 28 cycles with 65% and SSA3 of 5 cycles with 56%. In the present study Coulombic efficiency is concerned only for first cycle and it is noted that the TSA3 showed 71% than 66% and 62% respectively for SSA3 and ASA4.

Photocatalytic degradation of metoprolol tartrate in suspensions of two TiO2-based photocatalysts with different surface area. Identification of intermediates and proposal of degradation pathways

International Nuclear Information System (INIS)

Abramović, Biljana; Kler, Sanja; Šojić, Daniela; Laušević, Mila; Radović, Tanja; Vione, Davide

2011-01-01

Highlights: ► Kinetics and efficiency of photocatalytic degradation of the β 1 -blocker metoprolol tartrate (MET). ► Two TiO 2 specimens employed. ► Faster degradation of MET, but slower mineralization, obtained with the TiO 2 specimen having lower surface area. ► Photocatalytic transformation pathways of MET including mineralization. - Abstract: This study investigates the efficiency of the photocatalytic degradation of metoprolol tartrate (MET), a widely used β 1 -blocker, in TiO 2 suspensions of Wackherr's “Oxyde de titane standard” and Degussa P25. The study encompasses transformation kinetics and efficiency, identification of intermediates and reaction pathways. In the investigated range of initial concentrations (0.01–0.1 mM), the photocatalytic degradation of MET in the first stage of the reaction followed approximately a pseudo-first order kinetics. The TiO 2 Wackherr induced a significantly faster MET degradation compared to TiO 2 Degussa P25 when relatively high substrate concentrations were used. By examining the effect of ethanol as a scavenger of hydroxyl radicals (·OH), it was shown that the reaction with ·OH played the main role in the photocatalytic degradation of MET. After 240 min of irradiation the reaction intermediates were almost completely mineralized to CO 2 and H 2 O, while the nitrogen was predominantly present as NH 4 + . Reaction intermediates were studied in detail and a number of them were identified using LC–MS/MS (ESI+), which allowed the proposal of a tentative pathway for the photocatalytic transformation of MET as a function of the TiO 2 specimen.

Role of yttria-stabilized zirconia produced by ion-beam-assisted deposition on the properties of RuO2 on SiO2/Si

International Nuclear Information System (INIS)

Jia, Q.X.; Arendt, P.; Groves, J.R.; Fan, Y.; Roper, J.M.; Foltyn, S.R.

1998-01-01

Highly conductive biaxially textured RuO 2 thin films were deposited on technically important SiO 2 /Si substrates by pulsed laser deposition, where yttria-stabilized zirconia (YSZ) produced by ion-beam-assisted-deposition (IBAD) was used as a template to enhance the biaxial texture of RuO 2 on SiO 2 /Si. The biaxially oriented RuO 2 had a room-temperature resistivity of 37 μΩ-cm and residual resistivity ratio above 2. We then deposited Ba 0.5 Sr 0.5 TiO 3 thin films on RuO 2 /IBAD-YSZ/SiO 2 /Si. The Ba 0.5 Sr 0.5 TiO 3 had a pure (111) orientation normal to the substrate surface and a dielectric constant above 360 at 100 kHz. copyright 1998 Materials Research Society

Solution-deposited F:SnO₂/TiO₂ as a base-stable protective layer and antireflective coating for microtextured buried-junction H₂-evolving Si photocathodes.

Science.gov (United States)

Kast, Matthew G; Enman, Lisa J; Gurnon, Nicholas J; Nadarajah, Athavan; Boettcher, Shannon W

2014-12-24

Protecting Si photocathodes from corrosion is important for developing tandem water-splitting devices operating in basic media. We show that textured commercial Si-pn(+) photovoltaics protected by solution-processed semiconducting/conducting oxides (plausibly suitable for scalable manufacturing) and coupled to thin layers of Ir yield high-performance H2-evolving photocathodes in base. They also serve as excellent test structures to understand corrosion mechanisms and optimize interfacial electrical contacts between various functional layers. Solution-deposited TiO2 protects Si-pn(+) junctions from corrosion for ∼24 h in base, whereas junctions protected by F:SnO2 fail after only 1 h of electrochemical cycling. Interface layers consisting of Ti metal and/or the highly doped F:SnO2 between the Si and TiO2 reduce Si-emitter/oxide/catalyst contact resistance and thus increase fill factor and efficiency. Controlling the oxide thickness led to record photocurrents near 35 mA cm(-2) at 0 V vs RHE and photocathode efficiencies up to 10.9% in the best cells. Degradation, however, was not completely suppressed. We demonstrate that performance degrades by two mechanisms, (1) deposition of impurities onto the thin catalyst layers, even from high-purity base, and (2) catastrophic failure via pinholes in the oxide layers after several days of operation. These results provide insight into the design of hydrogen-evolving photoelectrodes in basic conditions, and highlight challenges.

Superhydrophilicity of TiO2 nano thin films

International Nuclear Information System (INIS)

Mohammadizadeh, M.R.; Ashkarran, A.A.

2007-01-01

Full text: Among the several oxide semiconductors, titanium dioxide has a more helpful role in our environmental purification due to its photocatalytic activity, photo-induced superhydrophilicity, and as a result of them non-toxicity, self cleaning, and antifogging effects. After the discovery of superhydrophilicity of titanium dioxide in 1997, several researches have been performed due to its nature and useful applications. The superhydrophilicity property of the surface allows water to spread completely across the surface rather than remains as droplets, thus making the surface antifog and easy-to-clean. The distinction of photo-induced catalytic and hydrophilicity properties of TiO 2 thin films has been accepted although, the origin of hydrophilicity property has not been recognized completely yet. TiO 2 thin films on soda lime glass were prepared by the sol-gel method and spin coating process. The calcination temperature was changed from 100 to 550 C. XRD patterns show increasing the content of polycrystalline anatase phase with increasing the calcination temperature. The AFM results indicate granular morphology of the films, which particle size changes from 22 to 166 nm by increasing the calcination temperature. The RBS, EDX and Raman spectroscopy of the films show the ratio of Ti:O∼0.5, and diffusion of sodium ions from substrate into the layer, by increasing the calcination temperature. The UV/Vis. spectroscopy of the films indicates a red shift by increasing the calcination temperature. The contact angle meter experiment shows that superhydrophilicity of the films depends on the formation of anatase crystal structure and diffused sodium content from substrate to the layer. The best hydrophilicity property was observed at 450 C calcination temperature, where the film is converted to a superhydrophilic surface after 10 minutes under 2mW/cm 2 UV irradiation. TiO 2 thin film on Si(111), Si(100), and quartz substrates needs less time to be converted to

Cytokine induction of sol–gel-derived TiO2 and SiO2 coatings on metallic substrates after implantation to rat femur

Science.gov (United States)

Urbanski, Wiktor; Marycz, Krzysztof; Krzak, Justyna; Pezowicz, Celina; Dragan, Szymon Feliks

2017-01-01

Material surface is a key determinant of host response on implanted biomaterial. Therefore, modification of the implant surface may optimize implant–tissue reactions. Inflammatory reaction is inevitable after biomaterial implantation, but prolonged inflammation may lead to adverse reactions and subsequent implant failure. Proinflammatory activities of cytokines like interleukin (IL)-1, IL-6, and tumor necrosis factor-alpha (TNF-α) are attractive indicators of these processes and ultimately characterize biocompatibility. The objective of the study was to evaluate local cytokine production after implantation of stainless steel 316L (SS) and titanium alloy (Ti6Al4V) biomaterials coated with titanium dioxide (TiO2) and silica (SiO2) coatings prepared by sol–gel method. Biomaterials were implanted into rat femur and after 12 weeks, bones were harvested. Bone–implant tissue interface was evaluated; immunohistochemical staining was performed to identify IL-6, TNF-α, and Caspase-1. Histomorphometry (AxioVision Rel. 4.6.3 software) of tissue samples was performed in order to quantify the cytokine levels. Both the oxide coatings on SS and Ti6Al4V significantly reduced cytokine production. However, the lowest cytokine levels were observed in TiO2 groups. Cytokine content in uncoated groups was lower in Ti6Al4V than in SS, although coating of either metal reduced cytokine production to similar levels. Sol–gel TiO2 or SiO2 coatings reduced significantly the production of proinflammatory cytokines by local tissues, irrespective of the material used as a substrate, that is, either Ti6Al4V or SS. This suggests lower inflammatory response, which directly points out improvement of materials’ biocompatibility. PMID:28280331

Thermal Annealing Effect on Optical Properties of Binary TiO2-SiO2 Sol-Gel Coatings

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Xiaodong Wang

2012-12-01

Full Text Available TiO2-SiO2 binary coatings were deposited by a sol-gel dip-coating method using tetrabutyl titanate and tetraethyl orthosilicate as precursors. The structure and chemical composition of the coatings annealed at different temperatures were analyzed by Raman spectroscopy and Fourier Transform Infrared (FTIR spectroscopy. The refractive indices of the coatings were calculated from the measured transmittance and reflectance spectra. An increase in refractive index with the high temperature thermal annealing process was observed. The Raman and FTIR results indicate that the refractive index variation is due to changes in the removal of the organic component, phase separation and the crystal structure of the binary coatings.

Density, thickness and composition measurements of TiO2 -SiO2 thin films by coupling X-ray reflectometry, ellipsometry and electron probe microanalysis-X

International Nuclear Information System (INIS)

Hodroj, A.; Roussel, H.; Crisci, A.; Robaut, F.; Gottlieb, U.; Deschanvres, J.L.

2006-01-01

Mixed TiO 2 -SiO 2 thin films were deposited by aerosol atmospheric CVD method by using di-acetoxi di-butoxi silane (DADBS) and Ti tetra-butoxide as precursors. By varying the deposition temperatures between 470 and 600 deg. C and the ratios between the Si and Ti precursors (Si/Ti) from 2 up to 16, films with different compositions and thicknesses were deposited. The coupled analysis of the results of different characterisation methods was used in order to determine the variation of the composition, the thickness and the density of the films. First EPMA measurements were performed at different acceleration voltages with a Cameca SX50 system. By analysing, with specific software, the evolution of the intensity ratio I x /I std versus the voltage, the composition and the mass thickness (product of density by the thickness) were determined. In order to measure independently the density, X-ray reflectometry experiments were performed. By analysing the value of the critical angle and the Kiessig fringes, the density and the thickness of the layers were determined. The refractive index and the thickness of the films were also measured by ellipsometry. By assuming a linear interpolation between the index value of the pure SiO 2 and TiO 2 films, the film composition was deduced from the refractive index value. XPS measurements were also performed in order to obtain an independent value of the composition. A good agreement between the ways to measure the density is obtained

Influence of interface layer on optical properties of sub-20 nm-thick TiO2 films

Science.gov (United States)

Shi, Yue-Jie; Zhang, Rong-Jun; Li, Da-Hai; Zhan, Yi-Qiang; Lu, Hong-Liang; Jiang, An-Quan; Chen, Xin; Liu, Juan; Zheng, Yu-Xiang; Wang, Song-You; Chen, Liang-Yao

2018-02-01

The sub-20 nm ultrathin titanium dioxide (TiO2) films with tunable thickness were deposited on Si substrates by atomic layer deposition (ALD). The structural and optical properties were acquired by transmission electron microscopy, atomic force microscopy and spectroscopic ellipsometry. Afterwards, a constructive and effective method of analyzing interfaces by applying two different optical models consisting of air/TiO2/Ti x Si y O2/Si and air/effective TiO2 layer/Si, respectively, was proposed to investigate the influence of interface layer (IL) on the analysis of optical constants and the determination of band gap of TiO2 ultrathin films. It was found that two factors including optical constants and changing components of the nonstoichiometric IL could contribute to the extent of the influence. Furthermore, the investigated TiO2 ultrathin films of 600 ALD cycles were selected and then annealed at the temperature range of 400-900 °C by rapid thermal annealing. Thicker IL and phase transition cause the variation of optical properties of TiO2 films after annealing and a shorter electron relaxation time reveals the strengthened electron-electron and electron-phonon interactions in the TiO2 ultrathin films at high temperature. The as-obtained results in this paper will play a role in other studies of high dielectric constants materials grown on Si substrates and in the applications of next generation metal-oxide-semiconductor devices.

Efficient catalytic ozonation by ruthenium nanoparticles supported on SiO2 or TiO2: Towards the use of a non-woven fiber paper as original support

KAUST Repository

Biard, Pierre-Franç ois; Werghi, Baraa; Soutrel, Isabelle; Orhand, Romain; Couvert, Annabelle; Denicourt-Nowicki, Audrey; Roucoux, Alain

2015-01-01

This work focuses on the use of Ru(0) nanoparticles as heterogeneous catalyst for ozone decomposition and radical production. In a first set of experiments, the nanoparticles have been deposited on two inorganic supports (TiO2 or SiO2) by a wet

Anti-reflecting and passivating coatings for silicon solar cells on a basis of SO2 and TiO2 layers

International Nuclear Information System (INIS)

Taurbaev, T.I.; Nikulin, V.Eh.; Shorin, V.F.; Topanov, B.G.; Dikhanbaev, K.K.

2002-01-01

An analysis of influence of passivating layer on performance of anti-reflection coating of solar cells is carried out. The introduction of passivating SiO 2 layer between a frontal surface of the solar cell and TiO 2 +SiO 2 anti-reflection coating increase total reflection. If a thickness of a passivating layer no more than 20 Angstrom an increase of reflection does not exceed 0.5 %. However, for effective passivation the thickness of the passivating layer has to be within 100-1000 Angstrom region, thus the interference contribution of the passivating layer becomes essential and the AC is necessary to calculate as triple system SiO 2 -TiO 2 -SiO 2 . Such the three layers system ensuring average coefficient of reflection less of 3.5 % in a range 0.4-1.1 μm if the thickness of passivating SiO 2 layer no more 200 Angstrom. For solar cells with passivating SiO 2 layer thickness of 100 Angstrom and protective glass of non-interference thickness the single layer AC from TiO 2 allows to receive average value of reflection coefficient for a spectral range 0.4-1.1 μm no more than 9.5 %. The introduction of two additional layers SiO 2 and TiO 2 allows to reduce this value on 2.0-3.0 %. The comparison of calculation and experimental results is given. (author)

Materiais SiO2-TiO2 para a degradação fotocatalítica de diuron

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Arthur Alaím Bernardes

2011-01-01

Full Text Available SiO2-TiO2 materials prepared by sol-gel method were evaluated in the photocatalytic degradation of diuron. The materials were prepared with and without surfactant cetyltrimethylammonium chloride at different temperatures (25, 50 and 100 ºC. The samples were characterized by N2 adsorption-desorption measurements, scanning electron microscopy, X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy and infrared diffuse reflectance spectroscopy. The results showed that the materials synthesized with the surfactant had higher surface areas and band-gap values similar to anatase. All materials were more active than the commercial catalyst P-25 and better performance was achieved using the surfactant in the material synthesis.

The effect of TiO2 on nucleation and crystallization of a Li2O-Al2O3-SiO2 glass investigated by XANES and STEM.

Science.gov (United States)

Kleebusch, Enrico; Patzig, Christian; Krause, Michael; Hu, Yongfeng; Höche, Thomas; Rüssel, Christian

2018-02-13

Glass ceramics based on Li 2 O/Al 2 O 3 /SiO 2 are of high economic importance, as they often show very low coefficients of thermal expansion. This enables a number of challenging applications, such as cooktop panels, furnace windows or telescope mirror blanks. Usually, the crystallization of the desired LAS crystal phases within the glasses must be tailored by a careful choice of crystallization schedule and type of nucleation agents to be used. The present work describes the formation of nanocrystalline TiO 2 within an LAS base composition that contains solely TiO 2 as nucleating agent. Using a combination of scanning transmission electron microscopy as well as X-ray absorption spectroscopy, it is found that a mixture of four- and six-fold coordinated Ti 4+ ions exists already within the glass. Heating of the glass to 740 °C immediately changes this ratio towards a high content of six-fold coordinated Ti, which accumulates in liquid-liquid phase-separation droplets. During the course of thermal treatment, these droplets eventually evolve into nanocrystalline TiO 2 precipitations, in which Ti 4+ is six-fold coordinated. Thus, it is shown that the nucleation of nanocrystalline TiO 2 is initiated by a gradual re-arrangement of the Ti ions in the amorphous, glassy matrix, from a four-fold towards a six-fold coordination.

Properties and Crystallization Phenomena in Li2Si2O5–Ca5(PO4)3F and Li2Si2O5–Sr5(PO4)3F Glass–Ceramics Via Twofold Internal Crystallization

Science.gov (United States)

Rampf, Markus; Dittmer, Marc; Ritzberger, Christian; Schweiger, Marcel; Höland, Wolfram

2015-01-01

The combination of specific mechanical, esthetic, and chemical properties is decisive for the application of materials in prosthodontics. Controlled twofold crystallization provides a powerful tool to produce special property combinations for glass–ceramic materials. The present study outlines the potential of precipitating Ca5(PO4)3F as well as Sr5(PO4)3F as minor crystal phases in Li2Si2O5 glass–ceramics. Base glasses with different contents of CaO/SrO, P2O5, and F− were prepared within the glasses of the SiO2–Li2O–K2O–CaO/SrO–Al2O3–P2O5–F system. Preliminary studies of nucleation by means of XRD and scanning electron microscopy (SEM) of the nucleated base glasses revealed X-ray amorphous phase separation phenomena. Qualitative and quantitative crystal phase analyses after crystallization were conducted using XRD in combination with Rietveld refinement. As a main result, a direct proportional relationship between the content of apatite-forming components in the base glasses and the content of apatite in the glass–ceramics was established. The microstructures of the glass–ceramics were investigated using SEM. Microstructural and mechanical properties were found to be dominated by Li2Si2O5 crystals and quite independent of the content of the apatite present in the glass–ceramics. Biaxial strengths of up to 540 MPa were detected. Ca5(PO4)3F and Sr5(PO4)3F influence the translucency of the glass–ceramics and, hence, help to precisely tailor the properties of Li2Si2O5 glass–ceramics. The authors conclude that the twofold crystallization of Li2Si2O5–Ca5(PO4)3F or Li2Si2O5–Sr5(PO4)3F glass–ceramics involves independent solid-state reactions, which can be controlled via the chemical composition of the base glasses. The influence of the minor apatite phase on the optical properties helps to achieve new combinations of features of the glass–ceramics and, hence, displays new potential for dental applications. PMID:26389112

Internal Friction and Young's Modulus Measurements on SiO2 and Ta2O5 Films Done with an Ultra-High Q Silicon-Wafer Suspension

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Granata M.

2015-04-01

Full Text Available In order to study the internal friction of thin films a nodal suspension system called GeNS (Gentle Nodal Suspension has been developed. The key features of this system are: i the possibility to use substrates easily available like silicon wafers; ii extremely low excess losses coming from the suspension system which allows to measure Q factors in excess of 2×108 on 3” diameter wafers; iii reproducibility of measurements within few percent on mechanical losses and 0.01% on resonant frequencies; iv absence of clamping; v the capability to operate at cryogenic temperatures. Measurements at cryogenic temperatures on SiO2 and at room temperature only on Ta2O5 films deposited on silicon are presented.

Synthesis and photocatalytic activity of Ce-doped TiO2 and TiO2 nanotubes

International Nuclear Information System (INIS)

Arruda, L.B.; Pereira, E.A.; Paula, F.R.; Lisboa Filho, P.N.

2016-01-01

Full text: One-dimensional nanostructures have been intensively studied, from the point of view of their synthesis and mechanisms of formation, as well as their applications in photonics, solar energy conversion, environmental and photocatalysis, since their properties due high surface area, electrical conductivity and light dispersion effects. Titanium dioxide (TiO2) nanoparticles have been demonstrated to be an effective multifunctional material especially when the particle size is less than 50 nm exhibit photoinduced activities that originate from the semiconductor band gap. TiO2 is semiconductor more used in photocatalysis, for this reason various properties have been thoroughly investigated in order to show that the photocatalytic activity and TiO2 reaction mechanism are influenced by structure, defects and impurities, surface morphology. and interfaces in addition to the concentration of dopants, such as rare-earth elements. Cerium ions, for example, vary between Ce4+ and Ce3 + oxidation state making the cerium oxide appear as CeO2 and Ce2O3 under oxidation and reduction conditions. These different electronic structures of Ce3+ (4f15d0) and Ce4+ (4f05d0) provide different catalytic and optical properties at the TiO2. In this work, samples of Ce-doped TiO2 and TiO2 were synthesized by alkali route, and its photocatalytic activity analyzed in order to create a relationship between the response obtained and the structure and morphology of each sample. Alkali route consists in submitting TiO2 (anatase) powder directly in medium of the NaOH (10M) and maintained at 120°C/20 hours by a glycerin bath with subsequent washed with water and HCl (0.1M) until reaching the desired pH. The synthesized samples were then studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The photocatalytic decomposition of rhodamine B (Rh.B) it was performed under UV irradiation and visible light in air. For the obtained

Synthesis and photocatalytic activity of Ce-doped TiO2 and TiO2 nanotubes

Energy Technology Data Exchange (ETDEWEB)

Arruda, L.B.; Pereira, E.A.; Paula, F.R.; Lisboa Filho, P.N. [Universidade Estadual Paulista Julio de Mesquita Filho (UNESP), SP (Brazil)

2016-07-01

Full text: One-dimensional nanostructures have been intensively studied, from the point of view of their synthesis and mechanisms of formation, as well as their applications in photonics, solar energy conversion, environmental and photocatalysis, since their properties due high surface area, electrical conductivity and light dispersion effects. Titanium dioxide (TiO2) nanoparticles have been demonstrated to be an effective multifunctional material especially when the particle size is less than 50 nm exhibit photoinduced activities that originate from the semiconductor band gap. TiO2 is semiconductor more used in photocatalysis, for this reason various properties have been thoroughly investigated in order to show that the photocatalytic activity and TiO2 reaction mechanism are influenced by structure, defects and impurities, surface morphology. and interfaces in addition to the concentration of dopants, such as rare-earth elements. Cerium ions, for example, vary between Ce4+ and Ce3 + oxidation state making the cerium oxide appear as CeO2 and Ce2O3 under oxidation and reduction conditions. These different electronic structures of Ce3+ (4f15d0) and Ce4+ (4f05d0) provide different catalytic and optical properties at the TiO2. In this work, samples of Ce-doped TiO2 and TiO2 were synthesized by alkali route, and its photocatalytic activity analyzed in order to create a relationship between the response obtained and the structure and morphology of each sample. Alkali route consists in submitting TiO2 (anatase) powder directly in medium of the NaOH (10M) and maintained at 120°C/20 hours by a glycerin bath with subsequent washed with water and HCl (0.1M) until reaching the desired pH. The synthesized samples were then studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The photocatalytic decomposition of rhodamine B (Rh.B) it was performed under UV irradiation and visible light in air. For the obtained

PHOTODEGRADATION OF ALIZARIN S DYE USING TiO2-ZEOLITE AND UV RADIATION

Directory of Open Access Journals (Sweden)

Karna Wijaya

2010-06-01

Full Text Available An investigation of Alizarin S photodegradation using TiO2-zeolite and UV radiation was performed. TiO2-zeolite was prepared by dispersing oligocations of titanium into suspension of zeolite. The suspension was stirred and then filtered to separate the solid phase from the filtrate. the solid phase was calcined by microwave oven at 800 Watt for 5 minutes to convert the oligocations into its oxide forms. The calcined product and unmodified zeolite were characterized using x-ray diffractometry, FT-IR spectrophotometry, X-ray fluorescence and gas sorption analysis methods to determine their physicochemical properties. Photocatalytic activity of TiO2-zeolite was tested on Alizarin S solution using following method: 50 mg of zeolite was dispersed into 25 mL of 10-4 M Alizarin S. The dispersion was irradiated using 365 nm UV light at room temperature on various irradiation times, i.e. 10, 20, 30, 40 and 60 minutes. At certain irradiation time, the dispersion was filtered and the filtrate was then analyzed its concentration using UV-Vis spectrophotometry method. Characterization results exhibited that the formation of TiO2 on internal as well as external surfaces of zeolite could not be detected  with x-ray diffractometry and FT-IR spectrophotometry, however determination of titanium using x-ray fluorescence analysis on the calcined product showed that the concentration of titanium was much higher than zeolite (0.22% on zeolite and 12.08% on TiO2-zeolite. Gas sorption analysis result indicated that the the calcination  resulted in the increase of specific surface area (16,31 m2/g on zeolite and 100.96 m2/g on TiO2-zeolite as well as total pore volume of calcined product (13.34 mL/Å/g on zeolite and 57.54 mL/Å/g on TiO2-zeolite. The result of photocatalytic activitiy study showed that ca 99 % of Alizarin S was degraded by TiO2-zeolite after UV irradiation for 60 min.   Keywords: TiO2-zeolite, photocatalytic, Alizarin S.

Crystallisation of Ba1-xSrxZn2Si2O7 from BaO/SrO/ZnO/SiO2 glass with different ZrO2 and TiO2 concentrations

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Vladislavova, Liliya; Kracker, Michael; Zscheckel, Tilman; Thieme, Christian; Rüssel, Christian

2018-04-01

The effect of different nucleation agents such as ZrO2 and TiO2 was investigated for a first time with respect to their crystallisation behaviour in the glass system BaO-SrO-ZnO-SiO2. In all studied glasses, a Ba1-xSrxZn2Si2O7 (0.1 ≤ x ≤ 0.9) solid solution crystallized. This phase was first described in 2015 to possess a similar structure as the high temperature phase of BaZn2Si2O7 and a thermal expansion close to zero or even negative. It may find applications e.g. as cook panels, telescope mirrors, and furnace windows. Kinetic parameters of the crystallisation process were determined by supplying different heating rates in a differential scanning calorimeter (DSC). The results were evaluated using the equations of Ozawa and Kissinger with respect to the activation energies. Furthermore, the Ozawa method was used for the determination of Avrami parameters, which provides further information on the nucleation and crystallisation processes. Scanning electron microscopy including electron backscatter diffraction (EBSD) was used to characterise the microstructure, to determine the crystallite size and the crystal orientation. For the characterisation of the occurring crystalline phases, X-ray diffraction was used.

Photocatalytic activities of heterostructured TiO2-graphene porous microspheres prepared by ultrasonic spray pyrolysis

International Nuclear Information System (INIS)

Yang, Jikai; Zhang, Xintong; Li, Bing; Liu, Hong; Sun, Panpan; Wang, Changhua; Wang, Lingling; Liu, Yichun

2014-01-01

Highlights: • USP method is used to prepare TiO 2 -graphene porous microspheres. • XPS shows GO sheets in the composites has been reduced to graphene. • TiO 2 -graphene microspheres display a red-shifted absorption edge. • PL spectra indicate graphene can accept the photoexcited electrons from TiO 2 . • TiO 2 -graphene shows higher photocatalytic activity than TiO 2 under solar light. -- Abstract: TiO 2 -graphene porous microspheres were prepared by ultrasonic spray pyrolysis (USP) of aqueous suspension of graphene oxide containing TiO 2 nanoparticles (Degussa P25). The composite microspheres were characterized with SEM, XPS, photoluminescence, Raman and UV–Vis absorption spectra. TiO 2 -graphene porous microspheres displayed higher photocatalytic activity for the degradation of methylene blue solution than pristine TiO 2 microspheres under the irradiation of Xe lamp, and the highest activity was obtained at a weight percentage of graphene around 1%. The effect of graphene on photocatalytic activity of porous microsphere was discussed in terms of the enhanced charge separation by TiO 2 -graphene heterojunction, increased absorption of the visible light, as well as the possible hindrance of mass transportation in microspheres

Thickness Dependent Optical Properties of Sol-gel based MgF2 – TiO2 Thin Films

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Siddarth Krishnaraja Achar

2018-04-01

Full Text Available MgF2 – TiO2 thin films were prepared by cost effective solgel technique onto glass substrates and optical parameters were determined by envelope technique. Thin films were characterized by optical transmission spectroscopy in the spectral range 290 – 1000 nm. The refractive index, extinction coefficient, Optical thickness and band gap dependency on thickness were evaluated. Thickness dependency of thin films showed direct allowed transition with band gap of 3.66 to 3.73 eV.

Nanocomposites of TiO2/cyanoethylated cellulose with ultra high dielectric constants

International Nuclear Information System (INIS)

Madusanka, Nadeesh; Shivareddy, Sai G; Hiralal, Pritesh; Choi, Youngjin; Amaratunga, Gehan A J; Eddleston, Mark D; Oliver, Rachel A

2016-01-01

A novel dielectric nanocomposite containing a high permittivity polymer, cyanoethylated cellulose (CRS) and TiO 2 nanoparticles was successfully prepared with different weight percentages (10%, 20% and 30%) of TiO 2 . The intermolecular interactions and morphology within the polymer nanocomposites were analysed. TiO 2 /CRS nanofilms on SiO 2 /Si wafers were used to form metal–insulator–metal type capacitors. Capacitances and loss factors in the frequency range of 1 kHz–1 MHz were measured. At 1 kHz CRS-TiO 2 nanocomposites exhibited ultra high dielectric constants of 118, 176 and 207 for nanocomposites with 10%, 20% and 30% weight of TiO 2 respectively, significantly higher than reported values of pure CRS (21), TiO 2 (41) and other dielectric polymer-TiO 2 nanocomposite films. Furthermore, all three CRS-TiO 2 nanocomposites show a loss factor <0.3 at 1 kHz and low leakage current densities (10 −6 –10 −7 A cm −2 ). Leakage was studied using conductive atomic force microscopy and it was observed that the leakage is associated with TiO 2 nanoparticles embedded in the CRS polymer matrix. A new class of ultra high dielectric constant hybrids using nanoscale inorganic dielectrics dispersed in a high permittivity polymer suitable for energy management applications is reported. (paper)

Design of flexible PANI-coated CuO-TiO2-SiO2 heterostructure nanofibers with high ammonia sensing response values

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Pang, Zengyuan; Nie, Qingxin; Lv, Pengfei; Yu, Jian; Huang, Fenglin; Wei, Qufu

2017-06-01

We report a room-temperature ammonia sensor with extra high response values and ideal flexibility, including polyaniline (PANI)-coated titanium dioxide-silicon dioxide (TiO2-SiO2) or copper oxide-titanium dioxide-silicon dioxide (CuO-TiO2-SiO2) composite nanofibers. Such flexible inorganic TiO2-SiO2 and CuO-TiO2-SiO2 composite nanofibers were prepared by electrospinning, followed by calcination. Then, in situ polymerization of aniline monomers was carried out with inorganic TiO2-SiO2 and CuO-TiO2-SiO2 composite nanofibers as templates. Gas sensing tests at room temperature indicated that the obtained CuO-TiO2-SiO2/PANI composite nanofibers had much higher response values to ammonia gas (ca. 45.67-100 ppm) than most of those reported before as well as the prepared TiO2-SiO2/PANI composite nanofibers here. These excellent sensing properties may be due to the P-N, P-P heterojunctions and a structure similar to field-effect transistors formed on the interfaces between PANI, TiO2, and CuO, which is p-type, n-type, and p-type semiconductor, respectively. In addition, the prepared free-standing CuO-TiO2-SiO2/PANI composite nanofiber membrane was easy to handle and possessed ideal flexibility, which is promising for potential applications in wearable sensors in the future.

Preparation of Transparent Bulk TiO2/PMMA Hybrids with Improved Refractive Indices via an in Situ Polymerization Process Using TiO2 Nanoparticles Bearing PMMA Chains Grown by Surface-Initiated Atom Transfer Radical Polymerization.

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Maeda, Satoshi; Fujita, Masato; Idota, Naokazu; Matsukawa, Kimihiro; Sugahara, Yoshiyuki

2016-12-21

Transparent TiO 2 /PMMA hybrids with a thickness of 5 mm and improved refractive indices were prepared by in situ polymerization of methyl methacrylate (MMA) in the presence of TiO 2 nanoparticles bearing poly(methyl methacrylate) (PMMA) chains grown using surface-initiated atom transfer radical polymerization (SI-ATRP), and the effect of the chain length of modified PMMA on the dispersibility of modified TiO 2 nanoparticles in the bulk hybrids was investigated. The surfaces of TiO 2 nanoparticles were modified with both m-(chloromethyl)phenylmethanoyloxymethylphosphonic acid bearing a terminal ATRP initiator and isodecyl phosphate with a high affinity for common organic solvents, leading to sufficient dispersibility of the surface-modified particles in toluene. Subsequently, SI-ATRP of MMA was achieved from the modified surfaces of the TiO 2 nanoparticles without aggregation of the nanoparticles in toluene. The molecular weights of the PMMA chains cleaved from the modified TiO 2 nanoparticles increased with increases in the prolonging of the polymerization period, and these exhibited a narrow distribution, indicating chain growth controlled by SI-ATRP. The nanoparticles bearing PMMA chains were well-dispersed in MMA regardless of the polymerization period. Bulk PMMA hybrids containing modified TiO 2 nanoparticles with a thickness of 5 mm were prepared by in situ polymerization of the MMA dispersion. The transparency of the hybrids depended significantly on the chain length of the modified PMMA on the nanoparticles, because the modified PMMA of low molecular weight induced aggregation of the TiO 2 nanoparticles during the in situ polymerization process. The refractive indices of the bulk hybrids could be controlled by adjusting the TiO 2 content and could be increased up to 1.566 for 6.3 vol % TiO 2 content (1.492 for pristine PMMA).

Effects of TiO2 nanoparticles on the NO2− levels in cell culture media analysed by Griess colorimetric methods

International Nuclear Information System (INIS)

Popescu, Traian; Lupu, Andreea R.; Diamandescu, Lucian; Tarabasanu-Mihaila, Doina; Teodorescu, Valentin S.; Raditoiu, Valentin; Purcar, Violeta; Vlaicu, Aurel M.

2013-01-01

The Griess assay has been used to determine the possible changes in the measured NO 2 − concentrations induced by TiO 2 nanoparticles in three types of nitrite-containing samples: aqueous NaNO 2 solutions with known concentrations, and two types of cell culture media—Roswell Park Memorial Institute medium (RPMI-1640) and Dulbecco’s Modified Eagle Medium (DMEM-F12) used either as delivered or enriched in NO 2 − by NaNO 2 addition. We have used three types of titania with average particle sizes between 10 and 30 nm: Degussa P25 and two other samples (undoped and Fe 3+ -doped anatase TiO 2 ) synthesised by a hydrothermal route in our laboratory. The structural, morphological, optical and physicochemical characteristics of the used materials have been studied by X-ray diffraction, transmission electron microscopy (EDX), Mössbauer spectroscopy, Brunauer–Emmett–Teller nitrogen adsorption, UV–Vis reflectance spectroscopy, dynamic light scattering and diffuse reflectance infrared Fourier transform spectroscopy. The opacity and sedimentation behaviour of the studied TiO 2 suspensions have been investigated by photometric attenuance measurements at 540 nm. To account for the photocatalytic properties of titania in a biologically relevant context, multiple Griess tests have been performed under controlled exposure to laboratory natural daylight illumination. The results show significant variations of light attenuance (associated with NO 2 − concentrations in the Griess test) depending on the opacity, sedimentation behaviour, NO 2 − adsorption and photocatalytic properties of the tested TiO 2 nanomaterials. These findings identify material characteristics recommended to be considered when analysing the results of Griess tests performed in biological studies involving TiO 2 nanoparticles.

Comparative Studies on Thermal Performance of Conic Cut Twist Tape Inserts with SiO2 and TiO2 Nanofluids

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Sami D. Salman

2015-01-01

Full Text Available This paper presents a comparison study on thermal performance conic cut twist tape inserts in laminar flow of nanofluids through a constant heat fluxed tube. Three tape configurations, namely, quadrant cut twisted tape (QCT, parabolic half cut twisted tape (PCT, and triangular cut twisted (VCT of twist ratio y = 2.93 and cut depth de = 0.5 cm were used with 1% and 2% volume concentration of SiO2/water and TiO2/water nanofluids. Typical twist tape with twist ratio of y = 2.93 was used for comparison. The results show that the heat transfer was enhanced by increasing of Reynolds number and nanoparticles concentration of nanofluid. The results have also revealed that the use of twist tape enhanced the heat transfer coefficient significantly and maximum heat transfer enhancement was achieved by the presence of triangular cut twist tape insert with 2% volume concentration of SiO2 nanofluid. Over the range investigated, the maximum thermal performance factor of 5.13 is found with the simultaneous use of the SiO2 nanofluid at 2% volume concentration VCT at Reynolds number of 220. Furthermore, new empirical correlations for Nusselt number, friction factor, and thermal performance factor are developed and reported.

Preparation and solar-light photocatalytic activity of TiO2 composites: TiO2/kaolin, TiO2/diatomite, and TiO2/zeolite

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Li, Y.; Li, S. G.; Wang, J.; Li, Y.; Ma, C. H.; Zhang, L.

2014-12-01

Three TiO2 loaded composites, TiO2/kaolin, TiO2/diatomite, and TiO2/zeolite, were prepared in order to improve the solar-light photocatalytic activity of TiO2. The results showed that the photocatalytic activity could obviously be enhanced by loading appropriate amount of inorganic mineral materials. Meanwhile, TiO2 content, heat-treatment temperature and heat-treatment time on the photocatalytic activity were reviewed. Otherwise, the effect of solar light irradiation time and dye concentration on the photocatalytic degradation of Acid Red B was investigated. Furthermore, the degradation mechanism and adsorption process were also discussed.

Interconnected TiO2 Nanowire Networks for PbS Quantum Dot Solar Cell Applications

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Fan Xu

2012-01-01

Full Text Available We present a simple method for the fabrication of an interconnected porous TiO2 nanostructured film via dip coating in a colloidal suspension of ultrathin TiO2 nanowires followed by high-temperature annealing. The spheroidization of the nanowires and the fusing of the loosely packed nanowire films at the contact points lead to the formation of nanopores. Using this interconnected TiO2 nanowire network for electron transport, a PbS/TiO2 heterojunction solar cell with a large short-circuit current of 2.5 mA/cm2, a Voc of 0.6 V, and a power conversion efficiency of 5.4% is achieved under 8.5 mW/cm2 white light illumination. Compared to conventional planar TiO2 film structures, these results suggest superior electron transport properties while still providing the large interfacial area between PbS quantum dots and TiO2 required for efficient exciton dissociation.

Structural, spectroscopic and cytotoxicity studies of TbF3@CeF3 and TbF3@CeF3@SiO2 nanocrystals

International Nuclear Information System (INIS)

Grzyb, Tomasz; Runowski, Marcin; Dąbrowska, Krystyna; Giersig, Michael; Lis, Stefan

2013-01-01

Terbium fluoride nanocrystals, covered by a shell, composed of cerium fluoride were synthesized by a co-precipitation method. Their complex structure was formed spontaneously during the synthesis. The surface of these core/shell nanocrystals was additionally modified by silica. The properties of TbF 3 @CeF 3 and TbF 3 @CeF 3 @SiO 2 nanocrystals, formed in this way, were investigated. Spectroscopic studies showed that the differences between these two groups of products resulted from the presence of the SiO 2 shell. X-ray diffraction patterns confirmed the trigonal crystal structure of TbF 3 @CeF 3 nanocrystals. High resolution transmission electron microscopy in connection with energy-dispersive X-ray spectroscopy showed a complex structure of the formed nanocrystals. Crystallized as small discs, ‘the products’, with an average diameter around 10 nm, showed an increase in the concentration of Tb 3+ ions from surface to the core of nanocrystals. In addition to photo-physical analyses, cytotoxicity studies were performed on HSkMEC (Human Skin Microvascular Endothelial Cells) and B16F0 mouse melanoma cancer cells. The cytotoxicity of the nanomaterials was neutral for the investigated cells with no toxic or antiproliferative effect in the cell cultures, either for normal or for cancer cells. This fact makes the obtained nanocrystals good candidates for biological applications and further modifications of the SiO 2 shell.Graphical Abstract

Effect of substrate type on the electrical and structural properties of TiO2 thin films deposited by reactive DC sputtering

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Cheng, Xuemei; Gotoh, Kazuhiro; Nakagawa, Yoshihiko; Usami, Noritaka

2018-06-01

Electrical and structural properties of TiO2 thin films deposited at room temperature by reactive DC sputtering have been investigated on three different substrates: high resistivity (>1000 Ω cm) float zone Si(1 1 1), float zone Si(1 0 0) and alkali free glass. As-deposited TiO2 films on glass substrate showed extremely high resistivity of (∼5.5 × 103 Ω cm). In contrast, lower resistivities of ∼2 Ω cm and ∼5 Ω cm were obtained for films on Si(1 1 1) and Si(1 0 0), respectively. The as-deposited films were found to be oxygen-rich amorphous TiO2 for all the substrates as evidenced by X-ray photoemission spectroscopy and X-ray diffraction. Subsequent annealing led to appearance of anatase TiO2 on Si but not on glass. The surface of as-deposited TiO2 on Si was found to be rougher than that on glass. These results suggest that the big difference of electrical resistivity of TiO2 would be related with existence of more anatase nuclei forming on crystalline substrates, which is consistent with the theory of charged clusters that smaller clusters tend to adopt the substrate structure.

Removal of pharmaceutically active compounds from synthetic and real aqueous mixtures and simultaneous disinfection by supported TiO2/UV-A, H2O2/UV-A, and TiO2/H2O2/UV-A processes.

Science.gov (United States)

Bosio, Morgana; Satyro, Suéllen; Bassin, João Paulo; Saggioro, Enrico; Dezotti, Márcia

2018-05-01

Pharmaceutically active compounds are carried into aquatic bodies along with domestic sewage, industrial and agricultural wastewater discharges. Psychotropic drugs, which can be toxic to the biota, have been detected in natural waters in different parts of the world. Conventional water treatments, such as activated sludge, do not properly remove these recalcitrant substances, so the development of processes able to eliminate these compounds becomes very important. Advanced oxidation processes are considered clean technologies, capable of achieving high rates of organic compounds degradation, and can be an efficient alternative to conventional treatments. In this study, the degradation of alprazolam, clonazepam, diazepam, lorazepam, and carbamazepine was evaluated through TiO 2 /UV-A, H 2 O 2 /UV-A, and TiO 2 /H 2 O 2 /UV-A, using sunlight and artificial irradiation. While using TiO 2 in suspension, best results were found at [TiO 2 ] = 0.1 g L -1 . H 2 O 2 /UV-A displayed better results under acidic conditions, achieving from 60 to 80% of removal. When WWTP was used, degradation decreased around 50% for both processes, TiO 2 /UV-A and H 2 O 2 /UV-A, indicating a strong matrix effect. The combination of both processes was shown to be an adequate approach, since removal increased up to 90%. H 2 O 2 /UV-A was used for disinfecting the aqueous matrices, while mineralization was obtained by TiO 2 -photocatalysis.

Amorphous TiO2 Shells: A Vital Elastic Buffering Layer on Silicon Nanoparticles for High-Performance and Safe Lithium Storage.

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Yang, Jianping; Wang, Yunxiao; Li, Wei; Wang, Lianjun; Fan, Yuchi; Jiang, Wan; Luo, Wei; Wang, Yang; Kong, Biao; Selomulya, Cordelia; Liu, Hua Kun; Dou, Shi Xue; Zhao, Dongyuan

2017-12-01

Smart surface coatings of silicon (Si) nanoparticles are shown to be good examples for dramatically improving the cyclability of lithium-ion batteries. Most coating materials, however, face significant challenges, including a low initial Coulombic efficiency, tedious processing, and safety assessment. In this study, a facile sol-gel strategy is demonstrated to synthesize commercial Si nanoparticles encapsulated by amorphous titanium oxide (TiO 2 ), with core-shell structures, which show greatly superior electrochemical performance and high-safety lithium storage. The amorphous TiO 2 shell (≈3 nm) shows elastic behavior during lithium discharging and charging processes, maintaining high structural integrity. Interestingly, it is found that the amorphous TiO 2 shells offer superior buffering properties compared to crystalline TiO 2 layers for unprecedented cycling stability. Moreover, accelerating rate calorimetry testing reveals that the TiO 2 -encapsulated Si nanoparticles are safer than conventional carbon-coated Si-based anodes. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Enhanced electrochemical properties of F-doped Li2MnSiO4/C for lithium ion batteries

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Wang, Chao; Xu, Youlong; Sun, Xiaofei; Zhang, Baofeng; Chen, Yanjun; He, Shengnan

2018-02-01

The Li2MnSiO4 as a novel cathode material for lithium ion batteries, performs high specific capacity, high thermal stability, low cost and etc. However, it suffers from relatively low electronic conductivity and lithium ion diffusion rate. Herein, we successfully introduce fluorine to Li2MnSiO4 (Li2MnSiO4-xFx, x = 0.00, 0.01, 0.03 and 0.05) to overcome these obstacles. The results show that F doping not only enlarges the lattice parameters but also decreases the particle size, synergistically improving the lithium ion diffusion of Li2MnSiO4. Moreover, F doping increase electronic conductivity of Li2MnSiO4/C by inhibiting the formation of C-O bonds in the carbon layers. Meanwhile, F doping improves the crystallinity and stabilizes the crystal structure of Li2MnSiO4. Finally, the Li2MnSiO3.97F0.03/C with the best electrochemical performances delivers the initial specific discharge capacity of 279 mA h g-1 at 25mA g-1 current density from 1.5 V to 4.8 V. Also, it maintains a higher capacity (201 mA h g-1) than F-free Li2MnSiO4 (145 mA h g-1) after 50 cycles.

Hydrothermal transformation of titanate nanotubes into single-crystalline TiO2 nanomaterials with controlled phase composition and morphology

International Nuclear Information System (INIS)

Xu, Yuanmei; Fang, Xiaoming; Xiong, Jian; Zhang, Zhengguo

2010-01-01

Single-crystalline TiO 2 nanomaterials were synthesized by hydrothermally treating suspensions of H-titanate nanotubes and characterized by XRD, TEM, and HRTEM. The effects of the pH values of the suspensions and the hydrothermal temperatures on the phase composition and morphology of the obtained TiO 2 nanomaterials were systematically investigated. The H-titanate nanotubes were predominately transformed into anatase nanoparticle with rhombic shape when the pH value was greater than or equal to 1.0, whereas primarily turned into rutile nanorod with two pyramidal ends at the pH value less than or equal to 0.5. We propose a possible mechanism for hydrothermal transformation of H-titanate nanotubes into single-crystalline TiO 2 nanomaterials. While the H-titanate nanotubes transform into tiny anatase nanocrystallites of ca. 3 nm in size, the formed nanocrystallites as an intermediate grow into the TiO 2 nanomaterials with controlled phase composition and morphology. This growth process involves the steps of protonation, oriented attachment, and Ostwald ripening.

Influence of TiO2 content on the crystallization and microstructure of machinable glass-ceramics

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Debasis Pradip Mukherjee

2016-03-01

Full Text Available Glasses based on the SiO2–Al2O3–MgO–K2O–B2O3–MgF2 system added with TiO2 were synthesized and characterized by differential scanning calorimetry (DSC, X-ray powder diffraction (XRD, Fourier transform infrared spectroscopy (FTIR and scanning electron microscopy (SEM techniques. The results showed that by increasing the TiO2 content, glass transition temperature (Tg, both the crystallization peak temperature (TpI and TpII and activation energy (E increased. The interconnected large blocky card-like crystals were identified as fluorophlogopite as a major crystalline phase for all three glass-ceramic specimens by (XRD and subsequently confirmed by SEM. The Vickers hardness (Hv value for glass-ceramic specimens decreases with progressively increasing TiO2 content (1–10 wt% and Titania containing MGT-3 glass-ceramic specimen with interconnected large blocky card-like fluorophlogopite mica crystals possess lower Hv (4.26 GPa as well as good machinability (m = 0.12 useable for machinable applications. The study shows that Titania promoted initial crystallization of glass and can be used as an effective nucleting agent.

Electrical response of electron selective atomic layer deposited TiO2‑x heterocontacts on crystalline silicon substrates

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Ahiboz, Doğuşcan; Nasser, Hisham; Aygün, Ezgi; Bek, Alpan; Turan, Raşit

2018-04-01

Integration of oxygen deficient sub-stoichiometric titanium dioxide (TiO2‑x) thin films as the electron transporting-hole blocking layer in solar cell designs are expected to reduce fabrication costs by eliminating high temperature processes while maintaining high conversion efficiencies. In this paper, we conducted a study to reveal the electrical properties of TiO2‑x thin films grown on crystalline silicon (c-Si) substrates by atomic layer deposition (ALD) technique. Effect of ALD substrate temperature, post deposition annealing, and doping type of the c-Si substrate on the interface states and TiO2‑x bulk properties were extracted by performing admittance (C-V, G-V) and current-voltage (J-V) measurements. Moreover, the asymmetry in C-V and J-V measurements between the p-n type and n-n TiO2‑x-c-Si heterojunction types were examined and the electron transport selectivity of TiO2‑x was revealed.

Crystallization kinetics of a soda lime silica glass with TiO2 addition

International Nuclear Information System (INIS)

De la Parra A, S. M.; Alvarez M, A.; Torres G, L. C.; Sanchez, E. M.

2009-01-01

Studies conducted into Na 2 O-CaO-3SiO 2 glass composition suggest that its phase transformation occurs from the surface towards the interior of the sample. In a study carried out in 1982, it was reported that no addition of nucleating agents modified the mechanism. Taking advantage of the disposition materials synthesized by nanotechnology, in this study TiO 2 in nanometer size was used with the idea that, because of its qualities, it could modify the crystallization mechanism. The glasses obtained as well as the thermally treated samples, were evaluated by the X-ray diffraction (XRD) powder method, differential thermal analysis (DTA), and by optical microscopy and high resolution transmission electron microscopy (HRTEM). Within the range of TiO 2 concentration studied (0 - 10 wt %), 10 wt % of TiO 2 considerably reduced the Na 2 O-2CaO-3SiO 2 phase crystallization process. The crystallization mechanism was not modified and TiO 2 did not form compounds with the matrix components. (Author)

Self assembly of SiO2-encapsulated carbon microsphere composites

International Nuclear Information System (INIS)

Yang Yongzhen; Song Jingjing; Han Yanxing; Guo Xingmei; Liu Xuguang; Xu Bingshe

2011-01-01

SiO 2 was firstly coated onto the surface of carbon microspheres (CMSs) using tetraethyl orthosilicate (TEOS) as precursor by Stoeber method. Then SiO 2 -encapsulated CMS (CMS-SiO 2 ) composites were self-assembled by vertical deposition, in which the effects of deposition temperature and suspension concentration on the quality of self-assembling film were investigated. Morphologies and structures of the samples were characterized by field emission scanning electron microscopy, Fourier transformation infrared spectrometry, X-ray diffraction and thermogravimetry. The results show that uniform CMS-SiO 2 composites with good mono-dispersion were prepared by Stober method with 0.5 g of CMSs, 2 mL of TEOS, 30 mL of ammonia and 12 h of reaction time, the CMSs-based films with ordered and denser structure were prepared by vertical deposition using CMS-SiO 2 composites as monodipersion spheres under suspension concentration of 1 wt% and deposition temperature of 50 deg. C. The ultraviolet-visible absorption measurement shows that the absorbance of CMS-SiO 2 composite films grew steadily with increasing suspension concentration.

Adsorption of F2C=CFCl on TiO2 nano-powder: Structures, energetics and vibrational properties from DRIFT spectroscopy and periodic quantum chemical calculations

International Nuclear Information System (INIS)

Tasinato, Nicola; Moro, Daniele; Stoppa, Paolo; Pietropolli Charmet, Andrea; Toninello, Piero; Giorgianni, Santi

2015-01-01

Graphical abstract: - Highlights: • Adsorption of F 2 C=CFCl on TiO 2 unveiled by DRIFTS and periodic DFT. • Structural, energetic and vibrational properties of F 2 C=CFCl @ anatase (1 0 1). • Binding energies (B3LYP-D2) between −17 and −46 kJ mol −1 depending on the anchor point. • Theory and experiment converge on the CF 2 moiety as the main anchor point. - Abstract: Photodegradation over titanium dioxide (TiO 2 ) is a very appealing technology for removing environmental pollutants from the air, the adsorption interaction being the first step of the whole reaction pathway. In the present work the adsorption of F 2 C=CFCl (chlorotrifluoroethene, halon 1113), a compound used by industry and detected in the atmosphere, on a commercial TiO 2 nano-powder is investigated experimentally by in situ DRIFT spectroscopy and theoretically through periodic ab initio calculations rooted in DFT. The spectra of the adsorbed molecule suggest that the anchoring to the surface mainly takes place through F atoms. Theoretically, five adsorption configurations for the molecule interacting with the anatase (1 0 1) surface are simulated at B3LYP level and for each of them, structures, binding energies and vibrational frequencies are derived. The interplay between theory and experiments shows the coexistence of different adsorption configurations, the foremost ones featuring the interaction of one F atom with a fivefold coordinated Ti 4+ of the surface. These two adsorption models, which mostly differ for the orientation of the adsorbate with respect to the surface, feature a binding energy of −45.6 and −41.0 kJ mol −1 according to dispersion corrected DFT calculations. The favorable adsorption interaction appears as an important requirement toward the application of titanium dioxide technologies for the photocatalytic degradation of halon 1113.

Thermal shock properties of 2D-SiCf/SiC composites

International Nuclear Information System (INIS)

Lee, Sang Pill; Lee, Jin Kyung; Son, In Soo; Bae, Dong Su; Kohyama, Akira

2012-01-01

This paper dealt with the thermal shock properties of SiC f /SiC composites reinforced with two dimensional SiC fabrics. SiC f /SiC composites were fabricated by a liquid phase sintering process, using a commercial nano-size SiC powder and oxide additive materials. An Al 2 O 3 –Y 2 O 3 –SiO 2 powder mixture was used as a sintering additive for the consolidation of SiC matrix region. In this composite system, Tyranno SA SiC fabrics were also utilized as a reinforcing material. The thermal shock test for SiC f /SiC composites was carried out at the elevated temperature. Both mechanical strength and microstructure of SiC f /SiC composites were investigated by means of optical microscopy, SEM and three point bending test. SiC f /SiC composites represented a dense morphology with a porosity of about 8.2% and a flexural strength of about 160 MPs. The characterization of SiC f /SiC composites was greatly affected by the history of cyclic thermal shock. Especially, SiC f /SiC composites represented a reduction of flexural strength at the thermal shock temperature difference higher than 800 °C.

Removal of Hazardous Pollutants from Wastewaters: Applications of TiO2-SiO2 Mixed Oxide Materials

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Shivatharsiny Rasalingam

2014-01-01

Full Text Available The direct release of untreated wastewaters from various industries and households results in the release of toxic pollutants to the aquatic environment. Advanced oxidation processes (AOP have gained wide attention owing to the prospect of complete mineralization of nonbiodegradable organic substances to environmentally innocuous products by chemical oxidation. In particular, heterogeneous photocatalysis has been demonstrated to have tremendous promise in water purification and treatment of several pollutant materials that include naturally occurring toxins, pesticides, and other deleterious contaminants. In this work, we have reviewed the different removal techniques that have been employed for water purification. In particular, the application of TiO2-SiO2 binary mixed oxide materials for wastewater treatment is explained herein, and it is evident from the literature survey that these mixed oxide materials have enhanced abilities to remove a wide variety of pollutants.

The degree of 5f electron localization in URu2Si2: electron energy-loss spectroscopy and spin-orbit sum rule analysis

Energy Technology Data Exchange (ETDEWEB)

Jeffries, J R; Moore, K T; Butch, N P; Maple, M B

2010-05-19

We examine the degree of 5f electron localization in URu{sub 2}Si{sub 2} using spin-orbit sum rule analysis of the U N{sub 4,5} (4d {yields} 5f) edge. When compared to {alpha}-U metal, US, USe, and UTe, which have increasing localization of the 5f states, we find that the 5f states of URu{sub 2}Si{sub 2} are more localized, although not entirely. Spin-orbit analysis shows that intermediate coupling is the correct angular momentum coupling mechanism for URu{sub 2}Si{sub 2} when the 5f electron count is between 2.6 and 2.8. These results have direct ramifications for theoretical assessment of the hidden order state of URu{sub 2}Si{sub 2}, where the degree of localization of the 5f electrons and their contribution to the Fermi surface are critical.

Preparation of sol-gel TiO2/purified Na-bentonite composites and their photovoltaic application for natural dye-sensitized solar cells

International Nuclear Information System (INIS)

Saelim, Ni-on; Magaraphan, Rathanawan; Sreethawong, Thammanoon

2011-01-01

Highlights: → Natural dye from red cabbage was successfully employed in DSSC. → A fast sol-gel method to produce TiO 2 /clay thin film was proposed. → The sol-gel-prepared TiO 2 /clay was applied as the scattering layer on top of TiO 2 electrode. → Thicker sol-gel-prepared TiO 2 /clay electrode showed higher DSSC efficiency. - Abstract: The sol-gel TiO 2 /purified natural clay electrodes having Ti:Si molar ratios of 95:5 and 90:10 were initially prepared, sensitized with natural red cabbage dye, and compared to the sol-gel TiO 2 electrode in terms of physicochemical characteristics and solar cell efficiency. The results showed that the increase in purified Na-bentonite content greatly increased the specific surface area and total pore volume of the prepared sol-gel TiO 2 /purified Na-bentonite composites because the clay platelets prevented TiO 2 particle agglomeration. The sol-gel TiO 2 /5 mol% Si purified Na-bentonite and sol-gel TiO 2 /10 mol% Si purified Na-bentonite composites could increase the film thickness of solar cells without cracking when they were coated as a scattering layer on the TiO 2 semiconductor-based film, leading to increasing the efficiency of the natural dye-sensitized solar cells in this work.

Microwave dielectric properties of low-fired Li_2TiO_3–MgO ceramics for LTCC applications

International Nuclear Information System (INIS)

Ma, Jian-Li; Fu, Zhi-Fen; Liu, Peng; Wang, Bing; Li, Yang

2016-01-01

Graphical abstract: This figure gives the Q × f and τ_f of Li_2TiO_3–MgO ceramics sintered at various temperatures with different LiF contents. Addition of LiF enhanced the sinterability and optimized the microwave dielectric properties of Li_2TiO_3–MgO ceramics. The excellent microwave dielectric properties (ε_r = 15.8, Q × f = 64,500 GHz, and τ_f = −0.2 ppm/°C) of Li_2TiO_3–MgO ceramics sintered at 850 °C illustrated that LiF is a simple effective sintering aids for Li_2TiO_3–MgO ceramics. Such sample was compatible with Ag electrodes, suitable for the low-temperature co-fired ceramics (LTCC) applications. - Highlights: • Temperature stability of Li_2TiO_3 ceramics were improved by doping MgO. • The low-fired Li_2TiO_3–MgO ceramics are fabricated. • LiF liquid phase reduced sintering temperature of Li_2TiO_3–MgO ceramics to 850 °C. • The low-fired Li_2TiO_3–MgO ceramics possess well microwave dielectric properties. • The sample was compatible with Ag electrodes and suitable for LTCC applications. - Abstract: We fabricated the low-fired Li_2TiO_3–MgO ceramics doped with LiF by a conventional solid-state route, and investigated systematically their sintering characteristics, microstructures and microwave dielectric properties. The results showed that temperature stability of Li_2TiO_3 ceramics were improved by doping MgO. Well microwave dielectric properties for Li_2TiO_3–13 wt%MgO (LTM) ceramics with ε_r = 16.4, Q × f = 87,500 GHz, and τ_f = −1.2 ppm/°C were obtained at 1325 °C. Furthermore, addition of LiF enhanced the sinterability and optimized the microwave dielectric properties of LTM ceramics. A typically sample of LTM-4 wt%LiF ceramics with optimum dielectric properties (ε_r = 15.8, Q × f = 64,500 GHz, and τ_f = −0.2 ppm/°C) were achieved at 850 °C for 4 h. Such sample was compatible with Ag electrodes, suitable for the low-temperature co-fired ceramics (LTCC) applications.

Fabricating TiO2 nanocolloids by electric spark discharge method at normal temperature and pressure.

Science.gov (United States)

Tseng, Kuo-Hsiung; Chang, Chaur-Yang; Chung, Meng-Yun; Cheng, Ting-Shou

2017-11-17

In this study, TiO 2 nanocolloids were successfully fabricated in deionized water without using suspending agents through using the electric spark discharge method at room temperature and under normal atmospheric pressure. This method was exceptional because it did not create nanoparticle dispersion and the produced colloids contained no derivatives. The proposed method requires only traditional electrical discharge machines (EDMs), self-made magnetic stirrers, and Ti wires (purity, 99.99%). The EDM pulse on time (T on ) and pulse off time (T off ) were respectively set at 50 and 100 μs, 100 and 100 μs, 150 and 100 μs, and 200 and 100 μs to produce four types of TiO 2 nanocolloids. Zetasizer analysis of the nanocolloids showed that a decrease in T on increased the suspension stability, but there were no significant correlations between T on and particle size. Colloids produced from the four production configurations showed a minimum particle size between 29.39 and 52.85 nm and a zeta-potential between -51.2 and -46.8 mV, confirming that the method introduced in this study can be used to produce TiO 2 nanocolloids with excellent suspension stability. Scanning electron microscopy with energy dispersive spectroscopy also indicated that the TiO 2 colloids did not contain elements other than Ti and oxygen.

Fabricating TiO2 nanocolloids by electric spark discharge method at normal temperature and pressure

Science.gov (United States)

Tseng, Kuo-Hsiung; Chang, Chaur-Yang; Chung, Meng-Yun; Cheng, Ting-Shou

2017-11-01

In this study, TiO2 nanocolloids were successfully fabricated in deionized water without using suspending agents through using the electric spark discharge method at room temperature and under normal atmospheric pressure. This method was exceptional because it did not create nanoparticle dispersion and the produced colloids contained no derivatives. The proposed method requires only traditional electrical discharge machines (EDMs), self-made magnetic stirrers, and Ti wires (purity, 99.99%). The EDM pulse on time (T on) and pulse off time (T off) were respectively set at 50 and 100 μs, 100 and 100 μs, 150 and 100 μs, and 200 and 100 μs to produce four types of TiO2 nanocolloids. Zetasizer analysis of the nanocolloids showed that a decrease in T on increased the suspension stability, but there were no significant correlations between T on and particle size. Colloids produced from the four production configurations showed a minimum particle size between 29.39 and 52.85 nm and a zeta-potential between -51.2 and -46.8 mV, confirming that the method introduced in this study can be used to produce TiO2 nanocolloids with excellent suspension stability. Scanning electron microscopy with energy dispersive spectroscopy also indicated that the TiO2 colloids did not contain elements other than Ti and oxygen.

Interface actions between TiO2 and porous diatomite on the structure and photocatalytic activity of TiO2-diatomite

Science.gov (United States)

Xia, Yue; Li, Fangfei; Jiang, Yinshan; Xia, Maosheng; Xue, Bing; Li, Yanjuan

2014-06-01

TiO2-diatomite photocatalysts were prepared by sol-gel process with various pre-modified diatomite. In order to obtain diatomite with different surface characteristics, two modification approaches including calcination and phosphoric acid treatment on the micro-structure of diatomite are introduced. The photocatalysts were characterized by XRD, XPS, nitrogen adsorption-desorption isotherms and micromorphology analysis. The results indicate that, compared with pure TiO2, the anatase-to-rutile phase transition temperature of TiO2 loaded on diatomite carrier is significantly increased to nearly 900 °C, depending on the different pretreatment method of diatomite. The photocatalytic activities of different samples were evaluated by their degradation rate of methyl orange (MO) dye under UV and visible-light irradiation. The samples prepared by phosphoric acid pretreatment method exhibit the highest photocatalytic activity. After 90 min of UV irradiation, about 90% of MO is decomposed by the best effective photocatalyst. And after 8 h visible-light irradiation, nearly 60% of MO is decomposed by the same sample. Further mechanism investigation reveals that the H3PO4 pretreatment process can obviously change the surface features of diatomite carrier, cause the formation of Si-O-Ti bond, increase the binding strength between TiO2 and diatomite, restrain crystal growth of loaded TiO2, and thus form thermal-stable mesoporous structure at the granular spaces. It helps to build micro-, meso- and macro-porous hierarchical porous structure in TiO2-diatomite, and improves the charge and mass transfer efficiency during catalyzing process, resulting in the significantly increased photocatalytic activity of TiO2-diatomite pretreated by phosphoric acid.

Structural analysis of molten Na2O-NaF-SiO2 system by Raman spectroscopy and molecular dynamics simulation

International Nuclear Information System (INIS)

Sasaki, Yasushi; Urata, Hidehiro; Ishii, Kuniyoshi

2003-01-01

To determine the effect of F ions on the structure of the molten alkali silicate systems, quenched Na 2 O-SiO 2 -NaF systems were investigated by Raman spectroscopy and molecular dynamics simulation. The systematic increase of 1100cm -1 band intensity in the Raman spectra of the silicate melts accompanying the replacement of O by F provides the evidence for concomitant polymerization of melts. From the molecular dynamics simulation, it was confirmed that most of substituted F was mainly coordinated to Na + ions but not Si 4+ ions at least up to 12.5 mol% of F ion content. A small amount of F was found to be coordinated to Si as a non-bridging ion from the molecular dynamics simulation, although there was no recognizable evidence from Raman Spectroscopy. These results were consistent with the mechanism in which F associated with otherwise network-modifying Na rather than with network-forming Si. Since F was associated to Na + ions, the replace of O ion by two F ions promote the polymerization of silicate melts. (author)

ELECTROPHORETIC DEPOSITION OF TIO2-MULTI-WALLED CARBON NANOTUBE COMPOSITE COATINGS: MORPHOLOGICAL STUDY

Directory of Open Access Journals (Sweden)

M. S. MAHMOUDI JOZEE

2016-09-01

Full Text Available A homogenous TiO2 / multi-walled carbon nanotubes(MWCNTs composite film were prepared by electrophoretic co-deposition from organic suspension on a stainless steel substrate.  In this study, MWCNTs was incorporated to the coating because of their long structure and their capability to be functionalized by different inorganic groups on the surface. FTIR spectroscopy showed the existence of carboxylic groups on the modified carbon nanotubes surface. The effect of applied electrical fields, deposition time and concentration of nanoparticulates on coatings morphology were investigated by scanning electron microscopy. It was found that combination of MWCNTs within TiO2 matrix eliminating micro cracks presented on TiO2 coating. Also, by increasing the deposition voltages, micro cracks were increased. SEM observation of the coatings revealed that TiO2/multi-walled carbon nanotubes coatings produced from optimized electric field was uniform and had good adhesive to the substrate.

Using TiO2 as a Conductive Protective Layer for Photocathodic H2 Evolution

DEFF Research Database (Denmark)

Seger, Brian; Pedersen, Thomas; Laursen, Anders Bo

2013-01-01

Surface passivation is a general issue for Si-based photoelectrodes because it progressively hinders electron conduction at the semiconductor/electrolyte interface. In this work, we show that a sputtered 100 nm TiO2 layer on top of a thin Ti metal layer may be used to protect an n+p Si photocatho...

Characterization and Comparison of Photocatalytic Activity Silver Ion doped on TiO2(TiO2/Ag+) and Silver Ion doped on Black TiO2(Black TiO2/Ag+)

Science.gov (United States)

Kim, Jin Yi; Sim, Ho Hyung; Song, Sinae; Noh, Yeoung Ah; Lee, Hong Woon; Taik Kim, Hee

2018-03-01

Titanium dioxide (TiO2) is one of the representative ceramic materials containing photocatalyst, optic and antibacterial activity. The hydroxyl radical in TiO2 applies to the intensive oxidizing agent, hence TiO2 is suitable to use photocatalytic materials. Black TiO2was prepared through reduction of amorphous TiO2 conducting under H2 which leads to color changes. Its black color is proven that absorbs 100% light across the whole-visible light, drawing enhancement of photocatalytic property. In this study, we aimed to compare the photocatalytic activity of silver ion doped on TiO2(TiO2/Ag+) and silver ion doped on black TiO2(black TiO2/Ag+) under visible light range. TiO2/Ag+ was fabricated following steps. 1) TiO2 was synthesized by a sol-gel method from Titanium tetraisopropoxide (TTIP). 2) Then AgNO3 was added during an aging process step for silver ion doping on the surface of TiO2. Moreover, Black TiO2/Ag+ was obtained same as TiO2/Ag+ except for calcination under H2. The samples were characterized X-ray diffraction (XRD), UV-visible reflectance (UV-vis DRS), and Methylene Blue degradation test. XRD analysis confirmed morphology of TiO2. The band gap of black TiO2/Ag+ was confirmed (2.6 eV) through UV-vis DRS, which was lower than TiO2/Ag+ (2.9 eV). The photocatalytic effect was conducted by methylene blue degradation test. It demonstrated that black TiO2/Ag+ had a photocatalytic effect under UV light also visible light.

Quantum-dot light-emitting diodes utilizing CdSe /ZnS nanocrystals embedded in TiO2 thin film

Science.gov (United States)

Kang, Seung-Hee; Kumar, Ch. Kiran; Lee, Zonghoon; Kim, Kyung-Hyun; Huh, Chul; Kim, Eui-Tae

2008-11-01

Quantum-dot (QD) light-emitting diodes (LEDs) are demonstrated on Si wafers by embedding core-shell CdSe /ZnS nanocrystals in TiO2 thin films via plasma-enhanced metallorganic chemical vapor deposition. The n-TiO2/QDs /p-Si LED devices show typical p-n diode current-voltage and efficient electroluminescence characteristics, which are critically affected by the removal of QD surface ligands. The TiO2/QDs /Si system we presented can offer promising Si-based optoelectronic and electronic device applications utilizing numerous nanocrystals synthesized by colloidal solution chemistry.

Synthesis of nanocomposite coating based on TiO2/ZnAl layer double hydroxides

International Nuclear Information System (INIS)

Jovanov, V.; Rudic, O.; Ranogajec, J.; Fidanchevska, E.

2017-01-01

The aim of this investigation was the synthesis of nanocomposite coatings based on Zn-Al layered double hydroxides (Zn-Al LDH) and TiO2. The Zn-Al LDH material, which acted as the catalyst support of the active TiO2 component (in the content of 3 and 10 wt. %), was synthesized by a low super saturation co-precipitation method. The interaction between the Zn-Al LDH and the active TiO2 component was accomplished by using vacuum evaporation prior to the mechanical activation and only by mechanical activation. The final suspension based on Zn-Al LDH and 10wt. % TiO2, impregnated only by mechanical activation, showed the optimal characteristics from the aspect of particle size distribution and XRD analysis. These properties had a positive effect on the functional properties of the coatings (photocatalytic activity and self-cleaning efficiency) after the water rinsing procedure. [es

X-ray diffraction studies of structures of Be, Al, LiF, Fe+3%Si, Si, SiO2, KCl under dynamic pressures from 2 Gpa to 20 Gpa

International Nuclear Information System (INIS)

Egorov, L.A.; Barenboim, A.I.; Mokhova, V.V.; Dorohin, V.V.; Samoilov, A.I.

1997-01-01

Currently, the only direct method to study behaviour of solid crystal substance structures under dynamic compression is method to record X-rays diffraction pictures of crystal structures under shock compression. Thepaper presents results of X-rays diffraction measurements concerning structural parameters of shock compressed substances at pressures higher than Hugoniot elastic limit (Be, Al, LiF, Fe+3%Si), lower than Hugoniot elastic limit (Si, SiO 2 , LiF) and in the area of pressures of phase transformation beginning (KCl, Si). Recorded states of shock-compressed substance structures demonstrate identity of structural deformations at pressures higher and lower than Hugoniot elastic limit as well as at pressures above the phase transformation point, which can be characterized as single-axial deformations. (orig.)

Enhancing the photocatalytic activity of nanocrystalline TiO2 by co-doping with fluorine and yttrium

International Nuclear Information System (INIS)

Zhang, Huarong; Miao, Guashuai; Ma, Xingping; Wang, Bei; Zheng, Haiwu

2014-01-01

Highlights: • (F, Y)-codoped TiO 2 nanoparticles were prepared by a simple sol–gel method. • The highest photocatalytic activity (15 times of that over the pure TiO 2 ) was exhibited in the codoped TiO 2 with 0.05% Y doping level. • The Y doping induced oxygen vancancies played a duel role on the photocatalyic activity of the codoped TiO 2 . • The photocatalytic reactive oxygen species are critical to the photocatalytic degradation processes. - Abstract: Fluorine and yttrium codoped TiO 2 nanoparticles were prepared using a simple sol–gel method. The products were characterized with various spectroscopic and analytical techniques to determine their structural, morphological, optical absorption and photocatalytic properties. The results reveal that neither F nor Y doping causes obvious absorption edge shift in TiO 2 . Photoluminescence (PL) emission spectra present that the PL signal is enhanced, suggesting a decrease of photo-generated charge carrier separation efficiency, after the F or Y doping. The synergistic action by the F and Y doping leads to the highest photocatalytic activity for the degradation of methylene blue solution in the 0.05% (F, Y)-codoped sample (15 times of that over the pure TiO 2 ). With the increase of Y doping level, the photocatalytic performance in the codoped samples increases firstly and then decreases. The photocatalytic activity variations after the F and Y doping were interpreted by the formation of photocatalytic reactive oxygen species induced by the dopings

Single-crystal X-ray diffraction study of Cs{sub 2}Er[Si{sub 6}O{sub 14}]F and Cs{sub 2}Er[Si{sub 4}O{sub 10}]F

Energy Technology Data Exchange (ETDEWEB)

Dabic, Predrag; Kremenovic, Aleksandar; Vulic, Predag [Belgrade Univ. (Serbia). Lab. of Crystallography; Kahlenberg, Volker; Schmidmair, Daniela [Innsbruck Univ. (Austria). Inst. of Mineralogy and Petrography

2016-07-01

Single-crystal growth experiments in the system CsF-Er{sub 2}O{sub 3}-SiO{sub 2} resulted in the simultaneous crystallization of two chemically related compounds within the same run: Cs{sub 2}Er[Si{sub 6}O{sub 14}]F (phase I) and Cs{sub 2}Er[Si{sub 4}O{sub 10}]F (phase II). They represent the first examples for cesium erbium silicates containing fluorine. Basic crystallographic data are - phase I: space group Cmca, a=17.2556(6) Aa, b=24.6565(7) Aa, c=14.4735(5) Aa, V=6157.9(3) Aa{sup 3}, Z=16; phase II: space group Pnma, a=22.3748(7) Aa, b=8.8390(2) Aa, c=11.9710(4) Aa, V=2367.5(1) Aa{sup 3}, Z=8. The structures were determined by direct methods and refined to residuals of R(vertical stroke F vertical stroke)=0.0229 for 2920 (phase I) and 0.0231 for 2314 (phase II) independent observed reflections with I>2σ(I). The structure of phase I represents a previously unknown structure type with a three dimensional tetrahedral framework consisting of Q{sup 3} and Q{sup 4} groups in the ratio 2:1. Basic building units of the network are unbranched sechser single-chains running parallel to [001]. The network can be conveniently built up from the condensation of tetrahedral layers parallel to (010) or (100), respectively. The crystal structure of phase II can be classified as a tubular or columnar chain silicate indicating that the backbones of the structure are multiple chains of silicate tetrahedra. This structure is isotypic to a Cs{sub 2}Y[Si{sub 4}O{sub 10}]F, a compound that has been characterized previously. Alternatively, both compounds can be described as mixed octahedral-tetrahedral frameworks, which can be classified according to their polyhedral microensembles. A topological analysis of both nets is presented.

Design and fabrication of a TiO2/nano-silicon composite visible light photocatalyst

International Nuclear Information System (INIS)

Lin, C.Y.; Fang, Y.K.; Kuo, C.H.; Chen, S.F.; Lin, C.-S.; Chou, T.H.; Lee, Y.-H.; Lin, J.-C.; Hwang, S.-B.

2006-01-01

Nano-silicon (nc-Si) was utilized as the charges generator to promote the photocatalytic and super-hydrophilic reactivity of TiO 2 film under visible light irradiation. The photocatalytic ability of TiO 2 /nc-Si composite photocatalyst was evaluated by a set of experiments to photodecompose 100 ppm methylene blue (MB) in aqueous solution. And the super-hydrophilic property was characterized by measuring the water droplet contacts angle, under visible light irradiation in atmospheric air and at room temperature. Under 100 mW/cm 2 visible light irradiation, the droplet contact angles were reduced to 0 deg. within 4 h with nc-Si charge generator. Additionally, the rate constant of MB photo-degradation was promoted 6.6 times

Films of brookite TiO2 nanorods/nanoparticles deposited by matrix-assisted pulsed laser evaporation as NO2 gas-sensing layers

Science.gov (United States)

Caricato, A. P.; Buonsanti, R.; Catalano, M.; Cesaria, M.; Cozzoli, P. D.; Luches, A.; Manera, M. G.; Martino, M.; Taurino, A.; Rella, R.

2011-09-01

Titanium dioxide (TiO2) nanorods in the brookite phase, with average dimensions of 3-4 nm × 20-50 nm, were synthesized by a wet-chemical aminolysis route and used as precursors for thin films that were deposited by the matrix-assisted pulsed laser evaporation (MAPLE) technique. A nanorod solution in toluene (0.016 wt% TiO2) was frozen at the liquid-nitrogen temperature and irradiated with a KrF excimer laser at a fluence of 350 mJ/cm2 and repetition rate of 10 Hz. Single-crystal Si wafers, silica slides, carbon-coated Cu grids and alumina interdigitated slabs were used as substrates to allow performing different characterizations. Films fabricated with 6000 laser pulses had an average thickness of ˜150 nm, and a complete coverage of the selected substrate as achieved. High-resolution scanning and transmission electron microscopy investigations evidenced the formation of quite rough films incorporating individually distinguishable TiO2 nanorods and crystalline spherical nanoparticles with an average diameter of ˜13 nm. Spectrophotometric analysis showed high transparency through the UV-Vis spectral range. Promising resistive sensing responses to 1 ppm of NO2 mixed in dry air were obtained.

Comparative study of neurologic effects of nano-TiO2 versus SiO2 after direct intracerebral exposure in mice

International Nuclear Information System (INIS)

Balvay, A; Bencsik, A; Thieriet, N; Lakhdar, L

2013-01-01

Titanium and silicon dioxide nanoparticles (TiO 2 and SiO 2 NPs) are now in daily use in many commercial products of which food, sunscreens, toothpastes or cosmetics. However, their effects on human body, especially on the central nervous system, are still unclear. The aim of this study was to determine whether direct exposition of the brain to TiO 2 and SiO 2 NPs results in alternations in nervous system function. C57Bl6 mice were exposed to 5 and 10 μg doses of TiO 2 and SiO 2 NPs through intracerebroventricular administration using a stereotaxic approach. Then the neurologic effects were investigated using motor performance parameters, measured on a rotarod at 20 rpm or at an accelerating rod (from 4 to 40 rpm). Before and after injection, motor activity is registered individually for each mouse exposed, once a week, for 8 weeks. Besides, a group of 3 mice is culled at 1, 2, 3, 4 and 8 weeks after exposure in order to study the time dependant effect on the histopathology of the brain (gliosis, inflammatory process...). Both rotarod tests (accelerating and at 20 rpm) showed that TiO 2 and SiO 2 NPs exposure could significantly impair the motor performances, even several weeks after initial acute exposure. The first examination of the brain histopathology revealed microglial activation. As it appeared to grow throughout the brain in a time dependant manner this suggests the induction of a long lasting neuroinflammation. These primary findings indicated that exposure to TiO 2 and SiO 2 NPs could possibly impair the locomotor ability and this deficit may be possibly attributed at least to an inflammatory process maintained till 8 weeks after exposure in the mouse brain. To fully investigate the neurotoxicological consequences of TiO 2 and SiO 2 NPs exposure, brain contents in these NPs will be also investigated as well as other alterations like neurotransmitter levels. These preliminary data already underline the necessity of more in vivo studies to better

Comparative study of neurologic effects of nano-TiO2 versus SiO2 after direct intracerebral exposure in mice

Science.gov (United States)

Balvay, A.; Thieriet, N.; Lakhdar, L.; Bencsik, A.

2013-04-01

Titanium and silicon dioxide nanoparticles (TiO2 and SiO2 NPs) are now in daily use in many commercial products of which food, sunscreens, toothpastes or cosmetics. However, their effects on human body, especially on the central nervous system, are still unclear. The aim of this study was to determine whether direct exposition of the brain to TiO2 and SiO2 NPs results in alternations in nervous system function. C57Bl6 mice were exposed to 5 and 10 μg doses of TiO2 and SiO2 NPs through intracerebroventricular administration using a stereotaxic approach. Then the neurologic effects were investigated using motor performance parameters, measured on a rotarod at 20 rpm or at an accelerating rod (from 4 to 40 rpm). Before and after injection, motor activity is registered individually for each mouse exposed, once a week, for 8 weeks. Besides, a group of 3 mice is culled at 1, 2, 3, 4 and 8 weeks after exposure in order to study the time dependant effect on the histopathology of the brain (gliosis, inflammatory process...). Both rotarod tests (accelerating and at 20 rpm) showed that TiO2 and SiO2 NPs exposure could significantly impair the motor performances, even several weeks after initial acute exposure. The first examination of the brain histopathology revealed microglial activation. As it appeared to grow throughout the brain in a time dependant manner this suggests the induction of a long lasting neuroinflammation. These primary findings indicated that exposure to TiO2 and SiO2 NPs could possibly impair the locomotor ability and this deficit may be possibly attributed at least to an inflammatory process maintained till 8 weeks after exposure in the mouse brain. To fully investigate the neurotoxicological consequences of TiO2 and SiO2 NPs exposure, brain contents in these NPs will be also investigated as well as other alterations like neurotransmitter levels. These preliminary data already underline the necessity of more in vivo studies to better characterize TiO2

Cytokine induction of sol–gel-derived TiO2 and SiO2 coatings on metallic substrates after implantation to rat femur

Directory of Open Access Journals (Sweden)

Urbanski W

2017-02-01

Full Text Available Wiktor Urbanski,1 Krzysztof Marycz,2 Justyna Krzak,3 Celina Pezowicz,4 Szymon Feliks Dragan1 1Department of Orthopaedic Surgery and Traumatology, Wroclaw University Hospital, 2Electron Microscope Laboratory, Wroclaw University of Environmental and Life Sciences, 3Institute of Materials Science and Applied Mechanics, 4Division of Biomedical Engineering and Experimental Mechanics, Wroclaw University of Technology, Wroclaw, Poland Abstract: Material surface is a key determinant of host response on implanted biomaterial. Therefore, modification of the implant surface may optimize implant–tissue reactions. Inflammatory reaction is inevitable after biomaterial implantation, but prolonged inflammation may lead to adverse reactions and subsequent implant failure. Proinflammatory activities of cytokines like interleukin (IL-1, IL-6, and tumor necrosis factor-alpha (TNF-α are attractive indicators of these processes and ultimately characterize biocompatibility. The objective of the study was to evaluate local cytokine production after implantation of stainless steel 316L (SS and titanium alloy (Ti6Al4V biomaterials coated with titanium dioxide (TiO2 and silica (SiO2 coatings prepared by sol–gel method. Biomaterials were implanted into rat femur and after 12 weeks, bones were harvested. Bone–implant tissue interface was evaluated; immunohistochemical staining was performed to identify IL-6, TNF-α, and Caspase-1. Histomorphometry (AxioVision Rel. 4.6.3 software of tissue samples was performed in order to quantify the cytokine levels. Both the oxide coatings on SS and Ti6Al4V significantly reduced cytokine production. However, the lowest cytokine levels were observed in TiO2 groups. Cytokine content in uncoated groups was lower in Ti6Al4V than in SS, although coating of either metal reduced cytokine production to similar levels. Sol–gel TiO2 or SiO2 coatings reduced significantly the production of proinflammatory cytokines by local tissues

TiO2 on magnesium silicate monolith: effects of different preparation techniques on the photocatalytic oxidation of chlorinated hydrocarbons

International Nuclear Information System (INIS)

Cardona, Ana I.; Candal, Roberto; Sanchez, Benigno; Avila, Pedro; Rebollar, Moises

2004-01-01

In this article, the comparative results of the photocatalytic oxidation of trichloroethylene (TCE) alone and a mixture of chlorinated hydrocarbons (trichloroethylene, perchloroethylene and chloroform) in gas phase, obtained with three different monolithic catalysts in a flat reactor frontally illuminated with a Xenon lamp are presented. The three catalysts incorporate titanium dioxide (TiO 2 ) as active phase on a magnesium silicate support, by means of different procedures: (i) incorporation of commercial TiO 2 powder into the silicate matrix ('massic monolith'); (ii) sol-gel coating of the silicate support; (iii) impregnation with a commercial TiO 2 aqueous suspension of the same silicate support. In the first case, the massic monolith was made from a 50:50 w/w mixture of magnesium silicate and 'Titafrance G5' TiO 2 powder. In the second case, a magnesium silicate monolith was coated with several layers of an aqueous TiO 2 sol prepared from hydrolysis and condensation of titanium tetra-isopropoxide (Ti(OC 3 H 7 ) 4 ) in excess of acidified water (acid catalysis). The third catalyst was prepared by impregnating the same silicate support with several layers of 'Titafrance G5' TiO 2 powder water suspension. All the catalysts were thermal treated under comparable conditions in order to fix the TiO 2 active phase to the silicate support. Although the performance of the massic monolith was better than the sol-gel monolith, the latter is of great interest because this technique allows the chemical composition of the active films to be easily modified

Optical properties of TiO2 nanotube arrays fabricated by the electrochemical anodization method

International Nuclear Information System (INIS)

Ly, Ngoc Tai; Nguyen, Van Chien; Dao, Thi Hoa; Hoang To, Le Hong; Pham, Duy Long; Do, Hung Manh; Vu, Dinh Lam; Le, Van Hong

2014-01-01

Perpendicularly self-aligned TiO 2 nanotube samples of size of 3 × 5 cm 2 were fabricated by the electrochemical anodization method using a solution containing NH 4 F. Influences of the technological conditions such as NH 4 F concentration and anodization voltage were studied. It was found that NH 4 F concentration in the solution and anodization voltage significantly affect the diameter and length of a TiO 2 nanotube. The diameter and the length of a TiO 2 nanotube were observed and estimated by using scanning electron microscopy. It has shown that the largest diameter and the longest length of about 80 nm and 20 μm, respectively, were obtained for the sample anodized in a solution containing 0.4% of NH 4 F, under a voltage of 48 V. Photoluminescence spectra excited by laser lights having wavelengths of 325 and 442 nm (having energies higher and lower than the band gap energy of TiO 2 ) was recorded at room temperature for the TiO 2 nanotube arrays. An abnormal luminescence result was observed. It is experimental evidence that the manufactured TiO 2 nanotube array is an expected material for hydrogen splitting from water by photochemical effect under sunlight as well as for the nano solar cells. (paper)

Preparation of Fluorine-Doped TiO2 Photocatalysts with Controlled Crystalline Structure

Directory of Open Access Journals (Sweden)

N. Todorova

2008-01-01

Full Text Available Nanocrystalline F-doped TiO2 powders were prepared by sol-gel route. The thermal behavior of the powders was recorded by DTA/TG technique. The crystalline phase of the fluorinated TiO2 powders was determined by X-ray diffraction technique. It was demonstrated that F-doping using CF3COOH favors the formation of rutile along with anatase phase even at low temperature. Moreover, the rutile's phase content increases with the increase of the quantity of the fluorine precursor in the starting solution. The surface area of the powders and the pore size distribution were studied by N2 adsorption-desorption using BET and BJH methods. X-ray photoelectron spectroscopy (XPS revealed that the fluorine is presented in the TiO2 powders mainly as metal fluoride in quantities ∼16 at %. The F-doped TiO2 showed a red-shift absorption in UV-vis region which was attributed to the increased content of rutile phase in the powders. The powders exhibited enhanced photocatalytic activity in decomposition of acetone.

Photocatalytic decomposition of N2O over TiO2/g-C3N4 photocatalysts heterojunction

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Kočí, K.; Reli, M.; Troppová, I.; Šihor, M.; Kupková, J.; Kustrowski, P.; Praus, P.

2017-02-01

TiO2/g-C3N4 photocatalysts with the various TiO2/g-C3N4 weight ratios from 1:2 to 1:6 were fabricated by mechanical mixing in water suspension followed by calcination. Pure TiO2 was prepared by thermal hydrolysis and pure g-C3N4 was prepared from commercial melamine by thermal annealing at 620 °C. All the nanocomposites were characterized by X-ray powder diffraction, UV-vis diffuse reflectance spectroscopy, Raman spectroscopy, infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, photoelectrochemical measurements and nitrogen physisorption. The prepared mixtures along with pure TiO2 and g-C3N4 were tested for the photocatalytic decomposition of nitrous oxide under UVC (λ = 254 nm), UVA (λ = 365 nm) and Vis (λ > 400 nm) irradiation. The TiO2/g-C3N4 nanocomposites showed moderate improvement compared to pure g-C3N4 but pure TiO2 proved to be a better photocatalyst under UVC irradiation. However, under UVA irradiation conditions, the photocatalytic activity of TiO2/g-C3N4 (1:2) nanocomposite exhibited an increase compared to pure TiO2. Nevertheless, further increase of g-C3N4 amount leads/led to a decrease in reactivity. These results are suggesting the nanocomposite with the optimal weight ratio of TiO2 and g-C3N4 have shifted absorption edge energy towards longer wavelengths and decreased the recombination rate of charge carriers compared to pure g-C3N4. This is probably due to the generation of heterojunction on the TiO2/g-C3N4 interface.

Study of application of Si2 and TiO2 nanofluids in electric oil transformers for performance analysis of thermal conductivity and dielectric rigidity

International Nuclear Information System (INIS)

Lopes, Daniel R.P.; Oliveira, Otávio L. de; Rocha, Marcelo da S.

2017-01-01

Electric transformers are essential equipment in the distribution of electrical energy as they are used for the continuous supply of electricity. For this reason it is important to study the possibilities of improving your insulation and cooling systems. The application of nanofluids in insulating mineral oils, which have a cooling and electrical insulation function, is a relevant issue in this area. In this work, the characteristics of the base mineral oil used in electric transformers with colloidal samples (nanofluids) made with the same base oil are compared using different concentrations of SiO 2 and TiO 2 nanoparticles. The characteristics of thermal conductivity and dielectric strength of nanofluid depend on nanoparticle concentrations, but the fluid must maintain all the insulation characteristics to be used in electrical transformers. The analysis will be performed through computational simulations using FEMM 2D software, applying its thermal conductivity module. The input data were taken from the characterization of samples produced with different concentrations of SiO 2 and TiO 2 nanoparticles (using the same mineral base oil). The parameters were applied in a computational model of a 50 kVA transformer, with usual geometry and natural circulation of oil (by convection) referencing electric transformers used in the market for energy conversion. This paper presents some of the results of a study of the dielectric properties and thermal conductivity of a mineral oil based nanofluid

An innovative approach to synthesize highly-ordered TiO2 nanotubes.

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Isimjan, Tayirjan T; Yang, D Q; Rohani, Sohrab; Ray, Ajay K

2011-02-01

An innovative route to prepare highly-ordered and dimensionally controlled TiO2 nanotubes has been proposed using a mild sonication method. The nanotube arrays were prepared by the anodization of titanium in an electrolyte containing 3% NH4F and 5% H2O in glycerol. It is demonstrated that the TiO2 nanostructures has two layers: the top layer is TiO2 nanowire and underneath is well-ordered TiO2 nanotubes. The top layer can easily fall off and form nanowires bundles by implementing a mild sonication after a short annealing time. We found that the dimensions of the TiO2 nanotubes were only dependent on the anodizing condition. The proposed technique may be extended to fabricate reproducible well-ordered TiO2 nanotubes with large area on other metals.

Pressure-Induced Polyamorphic Transition in Nanoscale TiO2

International Nuclear Information System (INIS)

Swamy, Varghese; Muddle, Barry C.

2009-01-01

The detection and characterization of pressure-induced amorphization in 20 GPa and ambient temperature is documented. The characterization employed in situ high-pressure angle-dispersive synchrotron X-ray diffraction and Raman spectroscopy in diamond-anvil cells. Comparative Raman spectroscopy allows the local structures of the high-density amorphous (HDA) form obtained at high pressures and its low-pressure (<10-15 GPa) low-density amorphous (LDA) analogue to be related to the baddeleyite-TiO2 and TiO2-II structures, respectively. The pressure-induced amorphization and the HDA-LDA transition in nanoscale TiO2 bear broad similarities to transitions in the Si and H2O systems.

Novel preparation and photocatalytic activity of one-dimensional TiO2 hollow structures

International Nuclear Information System (INIS)

Yu Huogen; Yu Jiaguo; Cheng Bei; Liu Shengwei

2007-01-01

Usually, templated methods include two important steps: the coating of nanocrystals on the surface of the templates and the removal of the templates. In this study, one-dimensional TiO 2 hollow structures, based on the template-directed deposition and then in situ template-sacrificial reaction (or dissolution), were prepared by a one-step template method using vanadium oxide nanobelts as the templates and TiF 4 as the precursor at 60 deg. C. The coating of TiO 2 nanoparticles on the surface of the templates was accompanied with the dissolution of vanadium oxide nanobelts by HF produced during the hydrolysis of TiF 4 in the reaction solution. It was found that the prepared one-dimensional TiO 2 hollow structures with a mesoporous wall were composed of TiO 2 nanoparticles with a diameter of 10-55 nm, resulting in a large specific surface area (77.2 m 2 g -1 ) and high pore volume (0.13 cm 3 g -1 ), and the wall thickness of the TiO 2 hollow structures could be easily controlled by adjusting the precursor concentration of TiF 4 . The photocatalytic activity experiment indicated that the prepared one-dimensional TiO 2 hollow structures, which could be readily separated from a slurry system after photocatalytic reaction, exhibited obvious photocatalytic activity for the photocatalytic degradation of methyl orange aqueous solution

Processing and optical properties of Nd3+-doped SiO2-TiO2-Al2O3 planar waveguides

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Xiang, Qing; Zhou, Yan; Ooi, Boon Siew; Lam, Yee Loy; Chan, Yuen Chuen; Kam, Chan Hin

2000-05-01

We report here the processing and optical characterization of Nd3+-doped SiO2-TiO2-Al2O3 planar waveguides deposited on SOS substrates by the sol-gel route combined with spin-coating and rapid thermal annealing. The recipes used for preparing the solutions by sol-gel route are in mole ratio of 93SiO2:20AlO1.5: x ErO1.5. In order to verify the residual OH content in the films, FTIR spectra were measured and the morphology of the material by the XRD analysis. Five 2-layer films annealed at a maximum temperature of 500 degrees C, 700 degrees C, 900 degrees, 1000 degrees C, 1100 degrees C respectively were fabricated on silicon. The FTIR and XRD curves show that annealing at 1050 degrees C for 15s effectively removes the OH in the materia and keeps the material amorphous. The propagation loss of the planar waveguides was measured by using the method based on scattering in measurements and the result was obtained to be 1.54dB/cm. The fluorescence spectra were measured with 514nm wavelength of Ar+ laser by directly shining the pump beam on the film instead of prism coupling. The results show that the 1 mole Nd3+ content recipe has the strongest emission efficiency among the four samples investigated.

Engineering of highly ordered TiO2 nanopore arrays by anodization

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Wang, Huijie; Huang, Zhennan; Zhang, Li; Ding, Jie; Ma, Zhaoxia; Liu, Yong; Kou, Shengzhong; Yang, Hangsheng

2016-07-01

Finite element analysis was used to simulate the current density distributions in the TiO2 barrier layer formed at the initial stage of Ti anodization. The morphology modification of the barrier layer was found to induce current density distribution change. By starting the anodization with proper TiO2 barrier layer morphology, the current density distribution can be adjusted to favor the formation of either nanotube arrays or nanopore arrays of anodic TiO2. We also found that the addition of sodium acetate into the electrolyte suppressed both the field-assisted chemical dissolution of TiO2 and the TiF62- hydrolysis induced TiO2 deposition during anodization, and thus further favored the nanopore formation. Accordingly, highly ordered anodic TiO2 nanopore arrays, similar to anodic aluminum oxide nanopore arrays, were successfully prepared.

TiO2 nanoparticles supported on the Fe3O4@SiO2 nanocomposites: a novel magnetic nanocatalyst for the synthesis of 2-aminothiazoles

International Nuclear Information System (INIS)

Safari, Javad; Abedi-Jazini, Zahra; Zarnegar, Zohre; Sadeghi, Masoud

2015-01-01

Nano TiO 2 supported on the Fe 3 O 4 @SiO 2 nanocomposites is introduced as a novel catalyst for the environmental synthesis of 2-aminothiazoles in PEG-200 as a green medium at room temperature. In this reaction, thiourea and N-bromosuccinimide were reacted with various ketones affording the desired 2-aminothiazole compounds. This green protocol has promising features for the reaction response such as simple procedure, high yields, and the ease of separation of pure product, short reaction time, and convenient manipulation. This catalyst was easily separated by an external magnet, and the recovered catalyst was reused several times without any significant loss of activity.Graphical abstract

TiO2 supported over porous silica photocatalysts for pesticide degradation using solar light: Part 2. Silica prepared using acrylic acid emulsion

International Nuclear Information System (INIS)

Phanikrishna Sharma, Mangalampalli V.; Durga Kumari, Valluri; Subrahmanyam, Machiraju

2010-01-01

An acrylic acid emulsion mixture is used for synthesis of novel porous silica (E-Si) material. The photocatalytic activity of TiO 2 under solar light irradiation for isoproturon (herbicide) degradation is drastically increased when dispersed over E-Si support using solid state dispersion (SSD) technique. The composite material is characterized by XRD, nitrogen adsorption-desorption isotherms, UV-vis DRS, SEM and TEM measurements. The photocatalytic activities of the composite catalysts are evaluated for different parameters. The 5 wt% TiO 2 /E-Si is found to be highly active for isoproturon degradation.

Lattice defects in rutile, TiO2

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Nakagawa, M.; Itoh, H.; Nakanishi, S.; Kondo, K.; Okada, M.; Atobe, K.

1991-01-01

Rutile, TiO 2 , having a relatively high melting point exhibits strong optical absorption after neutron irradiation (8 x 10 16 n f /cm 2 ) at 15K. The band peak is located near 0.96 μ, having a FWHM of 0.87 eV (at liquid nitrogen temperature). After inverse recovery at 120K, lattice defects due probably to F centers are annealed out at about 220K. (author)

Targeted partial surface modification with nano-SiO2@Li2CoPO4F as high-voltage cathode material for LIBs

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Chang, Caiyun; Huang, Zhipeng; Tian, Runsai; Jiang, Xinyu; Li, Chunsheng; Feng, Jijun

2017-10-01

Tuning whole/partial surface modification on cathode material with oxide material is a sought-after method to enhance the electrochemical performance in power storage field. Herein, nano-SiO2 targeted partial surface modified high voltage cathode material Li2CoPO4F has been successfully fabricated via a facile self-assembly process in silica dispersion at ambient temperature. With the aid of polar -OH groups attracted on the surface of SiO2 micelles, the nano-SiO2 preferentially nestle up along the borders and boundaries of Li2CoPO4F particles, where protection should be deployed with emphasis against the undesirable interactions between materials and electrolytes. Compared with pristine Li2CoPO4F, the SiO2 selectively modified Li2CoPO4F cathode materials, especially LCPF-3S, exhibit desirable electrochemical performances with higher discharge capacity, more outstanding cycle stability and favorable rate capability without any additional carbon involved. The greatly enhanced electrochemical properties can be attributed to the improved lithium-ion diffusion kinetics and structure tolerance during repeated lithiation/delithiation process. Such findings reveal a great potential of nano-SiO2 modified Li2CoPO4F as high energy cathode material for lithium ion batteries.

Enhanced supercapacitor performance using hierarchical TiO2 nanorod/Co(OH)2 nanowall array electrodes

International Nuclear Information System (INIS)

Ramadoss, Ananthakumar; Kim, Sang Jae

2014-01-01

Graphical abstract: - Highlights: • TiO 2 /Co(OH) 2 hierarchical nanostructure was prepared by a combination of hydrothermal and cathodic electrodeposition method. • Hierarchical nanostructure electrode exhibited a maximum capacitance of 274.3 mF cm −2 at a scan rate of 5 mV s −1 . • Combination of Co(OH) 2 nanowall with TiO 2 NR into a single system enhanced the electrochemical behavior of supercapacitor electrode. - Abstract: We report novel hierarchical TiO 2 nanorod (NR)/porous Co(OH) 2 nanowall array electrodes for high-performance supercapacitors fabricated using a two-step process that involves hydrothermal and electrodeposition techniques. Field-emission scanning electron microscope images reveal a bilayer structure consisting of TiO 2 NR arrays with porous Co(OH) 2 nanowalls. Compared with the bare TiO 2 NRs, the hierarchical TiO 2 NRs/Co(OH) 2 electrodes showed improved pseudocapacitive performance in a 2-M KOH electrolyte solution, exhibiting an areal specific capacitance of 274.3 mF cm −2 at a scan rate of 5 mV s −1 . The electrodes exhibited good stability, retaining 82.5% of the initial capacitance after 4000 cycles. The good pseudocapacitive performance of the hierarchical nanostructures is mainly due to the porous structure, which provides fast ion and electron transfer, a large surface area, short ion diffusion paths, and a favourable volume change during the cycling process

Study of System Pressure Dependence on n-TiO2/p-Si Hetrostructure for Photovoltaic Applications

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S. Ramezani Sani

2015-01-01

Full Text Available This study reports the fabrication of n-TiO2/p-Si hetrojunction by deposition of TiO2nanowires on p-Si substrate. The effect of system pressure and the current-voltage (I-V characteristics of n-TiO2/p-si hetrojunction were studied. The morphology of the samples was investigated by Field Emission Scanning Electron Microscopy (FESEM which confirms formation of TiO2 nanowires that their diameters increase with increasing the pressure of system. The I-V characteristics were measured to investigate the hetrojunction effects of under forward and reverse biases at different system pressure by sweeping in the voltage from 0 to +6 V, then to -6 V, and finally reaching 0 V. TiO2/Si diodes   in the system pressure 60 mbar and 30 mbar indicated that a p-n junction formed in the n-TiO2/p-Si hetrojunction. But as the system pressure increased to 1000 mbar, the I-V characteristics became inversed. This treatment can be scribed by the change of the energy band structure of TiO2.

Silicon isotope separation utilizing infrared multiphoton dissociation of Si2F6 irradiated with two-color CO2 laser light

International Nuclear Information System (INIS)

Yokoyama, Atsushi; Ohba, Hironori; Hashimoto, Masashi; Arai, Shigeyoshi

2002-01-01

Silicon isotope separation has been done by utilizing the Infrared Multiphoton Dissociation (IRMPD) of Si 2 F 6 irradiated with two-color CO 2 laser lights. The two-color excitation method improved the separation efficiency keeping the high enrichment factors. For example, 99.74% of 28 Si was obtained at 49.63% dissociation of Si 2 F 6 after the simultaneous irradiation of 200 pulses with 966.23 cm -1 photons (0.084 J/cm 2 ) and 954.55 cm -1 photons (0.658 J/cm 2 ), while 2000 pulses were needed to obtain 99.35% of 28 Si at 35.6% dissociation in the case of only one-color irradiation at 954.55 cm -1 (0.97 J/cm 2 ). (author)

Photoactive TiO2 Films Formation by Drain Coating for Endosulfan Degradation

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Natalia Tapia-Orozco

2013-01-01

Full Text Available Heterogeneous photocatalysis is an advanced oxidation process in which a photoactive catalyst, such as TiO2, is attached to a support to produce free radical species known as reactive oxygen species (ROS that can be used to break down toxic organic compounds. In this study, the draining time, annealing temperature, and draining/annealing cycles for TiO2 films grown by the drain coating method were evaluated using a 23 factorial experimental design to determine the photoactivity of the films via endosulfan degradation. The TiO2 films prepared with a large number of draining/annealing cycles at high temperatures enhanced (P>0.05 endosulfan degradation and superoxide radical generation after 30 minutes of illumination with UV light. We demonstrated a negative correlation (R2=0.69; P>0.01 between endosulfan degradation and superoxide radical generation. The endosulfan degradation rates were the highest at 30 minutes with the F6 film. In addition, films prepared using conditions F1, F4, and F8 underwent an adsorption/desorption process. The kinetic reaction constants, Kapp (min−1, were 0.0101, 0.0080, 0.0055, 0.0048, and 0.0035 for F6, F2, F5, F3, and F1, respectively. The endosulfan metabolites alcohol, ether, and lactone were detected and quantified at varying levels in all photocatalytic assays.

Quantum size effects in TiO2 thin films grown by atomic layer deposition

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Massimo Tallarida

2014-01-01

Full Text Available We study the atomic layer deposition of TiO2 by means of X-ray absorption spectroscopy. The Ti precursor, titanium isopropoxide, was used in combination with H2O on Si/SiO2 substrates that were heated at 200 °C. The low growth rate (0.15 Å/cycle and the in situ characterization permitted to follow changes in the electronic structure of TiO2 in the sub-nanometer range, which are influenced by quantum size effects. The modified electronic properties may play an important role in charge carrier transport and separation, and increase the efficiency of energy conversion systems.

Damage performance of TiO2/SiO2 thin film components induced by a long-pulsed laser

International Nuclear Information System (INIS)

Wang Bin; Dai Gang; Zhang Hongchao; Ni Xiaowu; Shen Zhonghua; Lu Jian

2011-01-01

In order to study the long-pulsed laser induced damage performance of optical thin films, damage experiments of TiO 2 /SiO 2 films irradiated by a laser with 1 ms pulse duration and 1064 nm wavelength are performed. In the experiments, the damage threshold of the thin films is measured. The damages are observed to occur in isolated spots, which enlighten the inducement of the defects and impurities originated in the films. The threshold goes down when the laser spot size decreases. But there exists a minimum threshold, which cannot be further reduced by decreasing the laser spot size. Optical microscopy reveals a cone-shaped cavity in the film substrate. Changes of the damaged sizes in film components with laser fluence are also investigated. The results show that the damage efficiency increases with the laser fluence before the shielding effects start to act.

The investigation of photo-induced chemiluminescence on Co2+-doped TiO2 nanoparticles and its analytical application.

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Li, Guixin; Nan, Hongyan; Zheng, Xingwang

2009-07-01

A novel space- and time-resolved photo-induced chemiluminescence (PICL) analytical method was developed based on the photocatalysis of the Co2+-doped TiO2 nanoparticles. The PICL reaction procedure under the photocatalysis of Co2+-doped TiO2 nanoparticles was investigated using cyclic voltammetry and potentiometry. Meanwhile, the effect of the electrical double layer outside the Co2+-doped TiO2 nanoparticles on the PICL was investigated by contrasting with the Co2+-doped TiO2-SiO2 core-shell nanoparticles. Significantly, the CL intensity increased apparently and the time of the CL was prolonged in the presence of procaterol hydrochloride because the mechanism of the enhanced PICL reaction may be modified. The route of the PICL was changed due to the participation of the procaterol hydrochloride enriched at the surface of the Co2+-doped TiO2-SiO2 in the PICL reaction, which prolonged the time of the CL reaction and resulted in the long-term PICL. The analytical characteristics of the proposed in-situ PICL method were investigated using the procaterol hydrochloride as the model analyte. The investigation results showed that this new PICL analytical method offered higher sensitivity to the analysis of the procaterol hydrochloride and the PICL intensity was linear with the concentration of the procaterol hydrochloride in the range from ca. 2.0 x 10(-10) to 1.0 x 10(-8) g mL(-1).

Efecto de las nanopartículas industriales TiO 2 , SiO 2 y ZnO sobre la viabilidad celular y expresión génica en médula ósea roja de mus musculus

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Jacquelyne Zarria-Romero

Full Text Available RESUMEN Objetivos Evaluar el efecto de las nanopartículas de ZnO, TiO2 y SiO2 sobre la viabilidad celular y la expresión génica de las interleuquinas 7 y 3 y del factor estimulante de colonias de granulocito - macrófago (GM-CSF en Mus musculus. Materiales y métodos Se extrajo médula ósea roja de cinco roedores (Balb/c para el estudio de viabilidad celular mediante la prueba de MTT. Por otro lado, grupos cinco roedores fueron inoculados vía intraperitoneal con dosis de 0,5; 1; 2,5; 5 y 10 mg/kg de nanopartículas de ZnO y SiO2 y de 5; 10; 15; 20 y 25 mg/kg de nanopartículas de TiO2, 30 h después, se obtuvo el ARN a partir de la médula ósea roja para los análisis de expresión génica empleando las técnicas de PCR y RT-PCR cuantitativa. Resultados Las nanopartículas de ZnO y SiO2 redujeron la viabilidad celular de una manera dosis-dependiente en un 37 y 26%, respectivamente, a partir de una dosis de 1 mg/kg. En cuanto al efecto sobre la expresión génica, a las dosis 5 y 10 mg/kg, las nanopartículas de TiO2 redujeron en mayor porcentaje la expresión de las interleuquinas 7 y 3 (55,3 y 70,2% respectivamente, con respecto a la expresión del GM-CSF, el mayor porcentaje de reducción lo produjo las nanopartículas de SiO2 (91%. Las nanopartículas de ZnO redujeron a partir de las dosis de 20 y 25 mg/kg. Conclusiones Las nanopartículas de ZnO, SiO2 y TiO2 alteran la viabilidad celular y la expresión génica en la médula ósea de ratón.

Aqueous Hg(2+) associates with TiO2 nanoparticles according to particle size, changes particle agglomeration, and becomes less bioavailable to zebrafish.

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Boran, Halis; Boyle, David; Altinok, Ilhan; Patsiou, Danae; Henry, Theodore B

2016-05-01

Engineered nanoparticles (NPs) have unique physicochemistry and potential to interact with other substances in the aqueous phase. Here, gene [metallothionein 2 (mt2)] expression changes in larval zebrafish were used to evaluate the association between aqueous Hg(2+) and TiO2 (NPs and bulk particle size control) to investigate the relationship between changes in Hg(2+) behavior and TiO2 size. During 24h exposures, TiO2 agglomerates increased in size and in the presence of 25μg Hg(2+)/L, greater increases in size were observed. The concentration of Hg(2+) in suspension also decreased in the presence of TiO2-NPs. Mercury increased expression of mt2 in larval zebrafish, but this response was lessened when zebrafish were exposed to Hg(2+) in the presence of TiO2-NPs, and which suggests that TiO2-NPs alter the bioavailability of Hg(2+) to zebrafish larvae. This ameliorative effect of TiO2 was also likely due to surface binding of Hg(2+) because a greater decrease in mt2 expression was observed in the presence of 1mg/L TiO2-NPs than 1mg/L TiO2-bulk. In conclusion, the results show that Hg(2+) will associate with TiO2-NPs, TiO2-NPs that have associated Hg(2+) will settle out of the aqueous phase more rapidly, and agglomerates will deliver associated Hg(2+) to sediment surfaces. Copyright © 2016 Elsevier B.V. All rights reserved.

Effect of titanium dioxide nanoparticles (TiO2 NPs) on the expression of mucin genes in human airway epithelial cells.

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Kim, Gui Ok; Choi, Yoon Seok; Bae, Chang Hoon; Song, Si-Youn; Kim, Yong-Dae

2017-01-01

Titanium dioxide nanoparticles (TiO 2 NPs) are utilized with growing frequency for a wide variety of industrial applications. Recently, acute and chronic exposures to TiO 2 NPs have been found to induce inflammatory response in the human respiratory tract. However, the effect and mechanism underlying the induction of major airway mucins by TiO 2 NPs have not been elucidated. This study was conducted to characterize the effect of TiO 2 NPs, and the mechanism involved, on the expressions of airway mucins in human airway epithelial cells. In NCI-H292 cells and primary cultures of normal nasal epithelial cells, the effects of TiO 2 NPs and signaling pathway for airway mucin genes were investigated by reverse transcriptase-polymerase chain reaction (RT-PCR), real-time PCR, enzyme immunoassays and immunoblot analysis using several specific inhibitors and small interfering RNAs (siRNAs). TiO 2 NPs increased MUC5B expression and activated the phosphorylations of extracellular signal-related kinase 1/2 (ERK1/2) and p38 mitogen-activated protein kinase (MAPK). U0126 (an ERK1/2 MAPK inhibitor) and SB203580 (a p38 MAPK inhibitor) inhibited TiO 2 NPs-induced MUC5B expression. And knockdown of ERK1, ERK2 and p38 MAPK using siRNAs significantly blocked TiO 2 NPs-induced MUC5B mRNA expression. Furthermore, Toll-like receptor 4 (TLR4) mRNA expression was increased by TiO 2 NPs, and knockdown by TLR4 siRNA significantly attenuated TiO 2 NPs-induced MUC5B mRNA expression and the TiO 2 NPs-induced phosphorylations of ERK1/2 and p38 MAPK. These results demonstrate for the first time that TiO 2 NPs induce MUC5B expression via TLR4-dependent ERK1/2 and p38 MAPK signaling pathways in respiratory epithelium.

Optical, Electrical, and Crystal Properties of TiO2 Thin Films Grown by Atomic Layer Deposition on Silicon and Glass Substrates

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Kupa, I.; Unal, Y.; Cetin, S. S.; Durna, L.; Topalli, K.; Okyay, A. K.; Ates, H.

2018-05-01

TiO2 thin films have been deposited on glass and Si(100) by atomic layer deposition (ALD) technique using tetrakis(diethylamido)titanium(IV) and water vapor as reactants. Thorough investigation of the properties of the TiO2/glass and TiO2/Si thin films was carried out, varying the deposition temperature in the range from 100°C to 250°C while keeping the number of reaction cycles fixed at 1000. Physical and material property analyses were performed to investigate optical and electrical properties, composition, structure, and morphology. TiO2 films grown by ALD may represent promising materials for future applications in optoelectronic devices.

Electrospinning processed nanofibrous TiO2 membranes for photovoltaic applications

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Onozuka, Katsuhiro; Ding, Bin; Tsuge, Yosuke; Naka, Takayuki; Yamazaki, Michiyo; Sugi, Shinichiro; Ohno, Shingo; Yoshikawa, Masato; Shiratori, Seimei

2006-02-01

We have recently fabricated dye-sensitized solar cells (DSSCs) comprising nanofibrous TiO2 membranes as electrode materials. A thin TiO2 film was pre-deposited on fluorine doped tin oxide (FTO) coated conducting glass substrate by immersion in TiF4 aqueous solution to reduce the electron back-transfer from FTO to the electrolyte. The composite polyvinyl acetate (PVac)/titania nanofibrous membranes can be deposited on the pre-deposited thin TiO2 film coated FTO by electrospinning of a mixture of PVac and titanium isopropoxide in N,N-dimethylformamide (DMF). The nanofibrous TiO2 membranes were obtained by calcining the electrospun composite nanofibres of PVac/titania as the precursor. Spectral sensitization of the nanofibrous TiO2 membranes was carried out with a ruthenium (II) complex, cis-dithiocyanate-N,N'-bis(2,2'-bipyridyl-4,4'-dicarboxylic acid) ruthenium (II) dihydrate. The results indicated that the photocurrent and conversion efficiency of electrodes can be increased with the addition of the pre-deposited TiO2 film and the adhesion treatment using DMF. Additionally, the dye loading, photocurrent, and efficiency of the electrodes were gradually increased by increasing the average thickness of the nanofibrous TiO2 membranes. The efficiency of the fibrous TiO2 photoelectrode with the average membrane thickness of 3.9 µm has a maximum value of 4.14%.

Cellular and molecular responses of E. fetida cœlomocytes exposed to TiO2 nanoparticles

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Bigorgne, Emilie; Foucaud, Laurent; Caillet, Céline; Giambérini, Laure; Nahmani, Johanne; Thomas, Fabien; Rodius, François

2012-07-01

An in vitro approach using cœlomocytes of Eisenia fetida was investigated to evaluate toxicity of TiO2 nanoparticles. Cœlomocytes were exposed to well-dispersed suspension of small aggregates (130 nm) of TiO2 nanoparticles (1-25 μg/ml) during 4, 12 and 24 h. Intracellular localisation suggested that the main route of uptake was endocytosis. Cellular responses showed that TiO2 nanoparticles were not cytotoxic and had no effect on phagocytosis at any of the four concentrations for each time tested. Concerning molecular responses, an increase of fetidin and metallothionein mRNA expression was observed starting from 4 h of exposure. In contrast, expression of coelomic cytolytic factor mRNA decreased for 10 and 25 μg/ml after 4 h. Superoxide dismutase, catalase and glutathione-S-transferase expression were not modified suggesting that oxidative stress was not induced by TiO2 in our experimental conditions. This in vitro approach showed that TiO2 nanoparticles were taken up by cœlomocytes and they could modify the molecular response of immune and detoxification system.

Review of Liquidus Surface and Phase Equilibria in the TiO2-SiO2-Al2O3-MgO-CaO Slag System at PO2 Applicable in Fluxed Titaniferous Magnetite Smelting

Science.gov (United States)

Goso, Xolisa; Nell, Johannes; Petersen, Jochen

The current liquidus surface and phase equilibria established in air for fluxed titaniferous magnetite (titanomagnetite) slags conforming to a composition of 37.19% TiO2, 19.69% SiO2, 13.12% Al2O3, and 30.00% of various ratios of CaO+MgO were reviewed at applicable PO2 using FactSage simulation and phase composition of a real plant titanomagnetite slag. The testwork included the incorporation into FactSage of a private MgTi2O5-Al2TiO5 pseudobrookite solution model. The results of the investigation showed that the liquidus surface and Ti3+/ Ti4+ mass fraction ratio increased with decreasing the PO2, At low PO2, perovskite crystallizes as a primary phase at high CaO content. The spinel solution, i.e. (Mg)(Al,Ti)O4, generally crystallizes as the primary phase at high MgO contents, though it is replaced by MgTi2O5-Al2TiO5 solution at PO2 of 10-10 atm to 10-15 atm. An intermediate equilibrium phase diagram established at PO2 of 10-16 atm is proposed. This phase diagram does not show the observed primary phase crystallization competition, however, the phase composition of a real titanomagnetite slag produced by Evraz Highveld Steel and Vanadium Corporation in South Africa does show primary phase crystallization competition between (Mg)(Al,Ti)2O4 and MgTi2O5-Al2TiO5. Smelting involving such slags is likely conducted around the transition PO2, i.e. PO2 of about 10-16 atm. Complex modelling with MgTi2O5, Al2TiO5 and Ti3O5 end members and experiments are underway to verify and update the intermediate phase diagram.

In-situ construction of Au nanoparticles confined in double-shelled TiO2/mSiO2 hollow architecture for excellent catalytic activity and enhanced thermal stability

Science.gov (United States)

Fang, Jiasheng; Zhang, Yiwei; Zhou, Yuming; Zhang, Chao; Zhao, Shuo; Zhang, Hongxing; Sheng, Xiaoli

2017-01-01

A facile strategy has been developed for the synthesis of H-TS-Au microspheres (MCs) with double-shelled hollow architecture and sub-5 nm Au nanoparticles (Au NPs). The synthetic procedure involves the successive sol-gel template-assisted method for the preparation of uniform hierarchical hollow-in-hollow H-TS MCs with TiO2/mSiO2 as yolks/shells, and the unique deposition-precipitation method mediated with Au(en)2Cl3 precursors for the in-situ construction of extremely stable Au NPs under a low-temperature hydrogen reduction. The synthesized H-TS-Au MCs were characterized by TEM, SEM, FTIR, XRD, BET and UV-vis absorption spectra. Catalytic activity of H-TS-Au was evaluated using the reduction of 4-nitrophenol (4-NP) into 4-aminophenol (4-AP) by NaBH4. Results established that H-TS-Au MCs possessed a large-size double-shelled architecture with high structural integrity and robustness,which can effectively confine numerous tiny Au NPs and restrict them from sintering aggregation even up to further calcination at 800 °C. Owing to the advantageous structural configuration and the synergistic effect of TiO2/mSiO2 double shells, the H-TS-Au MCs were demonstrated to exhibit a remarkable catalytic activity and stability, and preserve the intact morphology after 6 repeating reduction of 4-NP.

Synthesis, characterization, and thermal stability of SiO2/TiO2/CR-Ag multilayered nanostructures

Science.gov (United States)

Díaz, Gabriela; Chang, Yao-Jen; Philipossian, Ara

2018-06-01

The controllable synthesis and characterization of novel thermally stable silver-based particles are described. The experimental approach involves the design of thermally stable nanostructures by the deposition of an interfacial thick, active titania layer between the primary substrate (SiO2 particles) and the metal nanoparticles (Ag NPs), as well as the doping of Ag nanoparticles with an organic molecule (Congo Red, CR). The nanostructured particles were composed of a 330-nm silica core capped by a granular titania layer (10 to 13 nm in thickness), along with monodisperse 5 to 30 nm CR-Ag NPs deposited on top. The titania-coated support (SiO2/TiO2 particles) was shown to be chemically and thermally stable and promoted the nucleation and anchoring of CR-Ag NPs, which prevented the sintering of CR-Ag NPs when the structure was exposed to high temperatures. The thermal stability of the silver composites was examined by scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). Larger than 10 nm CR-Ag NPs were thermally stable up to 300 °C. Such temperature was high enough to destabilize the CR-Ag NPs due to the melting point of the CR. On the other hand, smaller than 10 nm Ag NPs were stable at temperatures up to 500 °C because of the strong metal-metal oxide binding energy. Energy dispersion X-ray spectroscopy (EDS) was carried out to qualitatively analyze the chemical stability of the structure at different temperatures which confirmed the stability of the structure and the existence of silver NPs at temperatures up to 500 °C.

Structural, spectroscopic and cytotoxicity studies of TbF{sub 3}@CeF{sub 3} and TbF{sub 3}@CeF{sub 3}@SiO{sub 2} nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Grzyb, Tomasz; Runowski, Marcin [Adam Mickiewicz University, Department of Rare Earths, Faculty of Chemistry (Poland); Dabrowska, Krystyna [Polish Academy of Sciences, Bacteriophage Laboratory, Institute of Immunology and Experimental Therapy (Poland); Giersig, Michael; Lis, Stefan, E-mail: blis@amu.edu.pl [Adam Mickiewicz University, Department of Rare Earths, Faculty of Chemistry (Poland)

2013-10-15

Terbium fluoride nanocrystals, covered by a shell, composed of cerium fluoride were synthesized by a co-precipitation method. Their complex structure was formed spontaneously during the synthesis. The surface of these core/shell nanocrystals was additionally modified by silica. The properties of TbF{sub 3}@CeF{sub 3} and TbF{sub 3}@CeF{sub 3}@SiO{sub 2} nanocrystals, formed in this way, were investigated. Spectroscopic studies showed that the differences between these two groups of products resulted from the presence of the SiO{sub 2} shell. X-ray diffraction patterns confirmed the trigonal crystal structure of TbF{sub 3}@CeF{sub 3} nanocrystals. High resolution transmission electron microscopy in connection with energy-dispersive X-ray spectroscopy showed a complex structure of the formed nanocrystals. Crystallized as small discs, 'the products', with an average diameter around 10 nm, showed an increase in the concentration of Tb{sup 3+} ions from surface to the core of nanocrystals. In addition to photo-physical analyses, cytotoxicity studies were performed on HSkMEC (Human Skin Microvascular Endothelial Cells) and B16F0 mouse melanoma cancer cells. The cytotoxicity of the nanomaterials was neutral for the investigated cells with no toxic or antiproliferative effect in the cell cultures, either for normal or for cancer cells. This fact makes the obtained nanocrystals good candidates for biological applications and further modifications of the SiO{sub 2} shell.Graphical Abstract.

Eu"2"+ doped TiO_2 nano structures synthesized by HYSYCVD for thermoluminescence dosimetry

International Nuclear Information System (INIS)

Perez A, J. A.; Leal C, A. L.; Melendrez A, R.; Barboza F, M.

2016-10-01

Titania (TiO_2) has attracted interest owing his potential applications as dosimetry material given his excellent optical, electrical and thermal properties and the ability to shape his structure make TiO_2 suitable for research and dosimetry applications. In this work, a systematic study to know the magnitude of processing parameters influence on thermoluminescent properties of undoped (TiO_2) and doped (TiO_2:Eu"2"+) nano materials obtained by hybrid precursor systems chemical vapor deposition (HYSYCVD) technique is presented. Synthesis of one dimension nano structures of TiO_2:Eu"2"+ was carried out using K_2TiF_6 and EuCl_2 as dopant at 0.5, 1, 2.5 and 5 wt %. The nano structures samples were irradiated with β-ray in a doses range of 0.083-3000 Gy. All thermoluminescence (Tl) glow curves showed 3 broad Tl peaks around 373, 473 and 573 K, and a dosimetric linear behavior from 0.083 to 300 Gy. The Tl has a good reproducibility, with deviations of around 5%, making these TiO_2:Eu"2"+ nano materials suitable for dosimetric applications. (Author)

Growth and characterization of nitrogen-doped TiO2 thin films prepared by reactive pulsed laser deposition

International Nuclear Information System (INIS)

Sauthier, G.; Ferrer, F.J.; Figueras, A.; Gyoergy, E.

2010-01-01

Nitrogen-doped titanium dioxide (TiO 2 ) thin films were grown on (001) SiO 2 substrates by reactive pulsed laser deposition. A KrF* excimer laser source (λ = 248 nm, τ FWHM ≅ 10 ns, ν = 10 Hz) was used for the irradiations of pressed powder targets composed by both anatase and rutile phase TiO 2 . The experiments were performed in a controlled reactive atmosphere consisting of oxygen or mixtures of oxygen and nitrogen gases. The obtained thin film crystal structure was investigated by X-ray diffraction, while their chemical composition as well as chemical bonding states between the elements were studied by X-ray photoelectron spectroscopy. An interrelation was found between nitrogen concentration, crystalline structure, bonding states between the elements, and the formation of titanium oxinitride compounds. Moreover, as a result of the nitrogen incorporation in the films a continuous red-shift of the optical absorption edge accompanied by absorption in the visible spectral range between 400 and 500 nm wavelength was observed.

Bioactivity studies on TiO2-bearing Na2O–CaO–SiO2–B2O3 glasses

International Nuclear Information System (INIS)

Jagan Mohini, G.; Sahaya Baskaran, G.; Ravi Kumar, V.; Piasecki, M.; Veeraiah, N.

2015-01-01

Soda lime silica borate glasses mixed with different concentrations of TiO 2 are synthesized by the melt-quenching technique. As a part of study on bioactivity of these glasses, the samples were immersed in simulated body fluid (SBF) solution for prolonged times (~ 21 days) during which weight loss along with pH measurements is carried out at specific intervals of time. The XRD and SEM analyses of post-immersed samples confirm the formation of crystalline hydroxyapatite layer (HA) on the surface of the samples. To assess the role of TiO 2 on the formation of HA layer and degradability of the samples the spectroscopic studies viz. optical absorption and IR spectral studies on post- and pre-immersed samples have been carried out. The analysis of the results of degradability together with spectroscopic studies as a function of TiO 2 concentration indicated that about 6.0 mol% of TiO 2 is the optimal concentration for achieving better bioactivity of these glasses. The presence of the maximal concentration octahedral titanium ions in this glass that facilitates the formation of HA layer is found to be the reason for such a higher bioactivity. - Highlights: • Soda lime silica borate glasses mixed with TiO 2 are synthesized. • Bioactivity of the glasses is studied by immersing them in SBF solution. • XRD and SEM studies indicated the formation of hydroxyapatite layer on the surface. • Quantum of degradability is the highest in the glasses mixed with 6.0 mol% of TiO 2. • The results are analyzed using IR and optical absorption studies

Synthesis of TiO2 nanoparticles containing Fe, Si, and V using multiple diffusion flames and catalytic oxidation capability of carbon-coated nanoparticles

KAUST Repository

Ismail, Mohamed; Memon, Nasir K.; Hedhili, Mohamed N.; Anjum, Dalaver H.; Chung, Suk-Ho

2016-01-01

Titanium dioxide (TiO2) nanoparticles containing iron, silicon, and vanadium are synthesized using multiple diffusion flames. The growth of carbon-coated (C–TiO2), carbon-coated with iron oxide (Fe/C–TiO2), silica-coated (Si–TiO2), and vanadium-doped (V–TiO2) TiO2 nanoparticles is demonstrated using a single-step process. Hydrogen, oxygen, and argon are utilized to establish the flame, with titanium tetraisopropoxide (TTIP) as the precursor for TiO2. For the growth of Fe/C–TiO2 nanoparticles, TTIP is mixed with xylene and ferrocene. While for the growth of Si–TiO2 and V–TiO2, TTIP is mixed with hexamethyldisiloxane (HMDSO) and vanadium (V) oxytriisopropoxide, respectively. The synthesized nanoparticles are characterized using high-resolution transmission electron microscopy (HRTEM) with energy-filtered TEM for elemental mapping (of Si, C, O, and Ti), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), nitrogen adsorption BET surface area analysis, and thermogravimetric analysis. Anatase is the dominant phase for the C–TiO2, Fe/C–TiO2, and Si–TiO2 nanoparticles, whereas rutile is the dominant phase for the V–TiO2 nanoparticles. For C–TiO2 and Fe/C–TiO2, the nanoparticles are coated with about 3-5-nm thickness of carbon. The iron-based TiO2 nanoparticles significantly improve the catalytic oxidation of carbon, where complete oxidation of carbon occurs at a temperature of 470 °C (with iron) compared to 610 °C (without iron). Enhanced catalytic oxidation properties are also observed for model soot particles, Printex-U, when mixed with Fe/C-TiO2. With regards to Si–TiO2 nanoparticles, a uniform coating of 3 to 8 nm of silicon dioxide is observed around the TiO2 particles. This coating mainly occurs due to variance in the chemical reaction rates of the precursors. Finally, with regards to V–TiO2, vanadium is doped within the TiO2 nanoparticles as visualized by HRTEM and XPS further confirms the formation of

Synthesis of TiO2 nanoparticles containing Fe, Si, and V using multiple diffusion flames and catalytic oxidation capability of carbon-coated nanoparticles

KAUST Repository

Ismail, Mohamed

2016-01-19

Titanium dioxide (TiO2) nanoparticles containing iron, silicon, and vanadium are synthesized using multiple diffusion flames. The growth of carbon-coated (C–TiO2), carbon-coated with iron oxide (Fe/C–TiO2), silica-coated (Si–TiO2), and vanadium-doped (V–TiO2) TiO2 nanoparticles is demonstrated using a single-step process. Hydrogen, oxygen, and argon are utilized to establish the flame, with titanium tetraisopropoxide (TTIP) as the precursor for TiO2. For the growth of Fe/C–TiO2 nanoparticles, TTIP is mixed with xylene and ferrocene. While for the growth of Si–TiO2 and V–TiO2, TTIP is mixed with hexamethyldisiloxane (HMDSO) and vanadium (V) oxytriisopropoxide, respectively. The synthesized nanoparticles are characterized using high-resolution transmission electron microscopy (HRTEM) with energy-filtered TEM for elemental mapping (of Si, C, O, and Ti), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), nitrogen adsorption BET surface area analysis, and thermogravimetric analysis. Anatase is the dominant phase for the C–TiO2, Fe/C–TiO2, and Si–TiO2 nanoparticles, whereas rutile is the dominant phase for the V–TiO2 nanoparticles. For C–TiO2 and Fe/C–TiO2, the nanoparticles are coated with about 3-5-nm thickness of carbon. The iron-based TiO2 nanoparticles significantly improve the catalytic oxidation of carbon, where complete oxidation of carbon occurs at a temperature of 470 °C (with iron) compared to 610 °C (without iron). Enhanced catalytic oxidation properties are also observed for model soot particles, Printex-U, when mixed with Fe/C-TiO2. With regards to Si–TiO2 nanoparticles, a uniform coating of 3 to 8 nm of silicon dioxide is observed around the TiO2 particles. This coating mainly occurs due to variance in the chemical reaction rates of the precursors. Finally, with regards to V–TiO2, vanadium is doped within the TiO2 nanoparticles as visualized by HRTEM and XPS further confirms the formation of

In situ study of interface reactions of ion beam sputter deposited (Ba0.5Sr0.5)TiO3 films on Si, SiO2, and Ir

International Nuclear Information System (INIS)

Gao, Y.; Mueller, A.H.; Irene, E.A.; Auciello, O.; Krauss, A.; Schultz, J.A.

1999-01-01

(Ba 0.5 ,Sr 0.5 )TiO 3 (BST) thin films were deposited on MgO, Si, SiO 2 and Ir surfaces by ion beam sputter deposition in oxygen at 700 degree C. In situ spectroscopic ellipsometry (SE) has been used to investigate the evolution of the BST films on different surfaces during both deposition and postannealing processes. First, the optical constants of the BST films in the photon energy range of 1.5 - 4.5 eV were determined by SE analysis on crystallized BST films deposited on MgO single crystal substrates. The interfaces in BST/Si and BST/SiO 2 /Si structure were examined by SE and Auger electron spectroscopy depth profiles. Subcutaneous oxidation in the BST/Ir structure was observed by in situ SE during both ion beam sputter deposition and postdeposition annealing in oxygen at 700 degree C. A study of the thermal stability of the Ir/TiN/SiO 2 /Si structure in oxygen at 700 degree C was carried out using in situ SE. The oxidation of Ir was confirmed by x-ray diffraction. The surface composition and morphology evolution after oxidation were investigated by time of flight mass spectroscopy of recoiled ions (TOF-MSRI) and atomic force microscopy. It has been found that Ti from the underlying TiN barrier layer diffused through the Ir layer onto the surface and thereupon became oxidized. It was also shown that the surface roughness increases with increasing oxidation time. The implications of the instability of Ir/TiN/SiO 2 /Si structure on the performance of capacitor devices based on this substrate are discussed. It has been shown that a combination of in situ SE and TOF-MSRI provides a powerful methodology for in situ monitoring of complex oxide film growth and postannealing processes. copyright 1999 American Vacuum Society

SiO2, TiO2 and Al2O3 colloid characterization and their cesium and iodine sorption part

International Nuclear Information System (INIS)

Hakem, N.

1995-03-01

Recent studies have shown the important role played by colloids in the transport behaviour of radionuclides. In the present study, we have investigated the sorption, at tracer level, to two radionuclides 131 I and 137 Cs on some mineral oxide colloids (100 to 500 nm in size) chosen as ''models'' owing to their very distinct isoelectric points; SiO 2 , TiO 2 and A1 2 O 3 (i.e.p. = 2, 6,25, 9,5 respectively). These colloids have first been characterized, under various pH and ionic strength conditions, by potentiometric and electro kinetic measurements. We have then measured the sorption ratios R, resulting from the partition, at equilibrium, of each radionuclide between the colloidal and aqueous phases in the contact. In a second step, we have attempted to describe the sorption mechanisms of iodine and cesium on the three oxide colloids under investigation, using following models: ion-exchange reaction, physical adsorption, Langmuir and Freundlich isotherms and surface complexation theories. (author). 53 refs., 13 tabs., 43 figs., 4 appendixes

Enhanced photoelectrochemical efficiency and stability using a conformal TiO2 film on a black silicon photoanode

Science.gov (United States)

Yu, Yanhao; Zhang, Zheng; Yin, Xin; Kvit, Alexander; Liao, Qingliang; Kang, Zhuo; Yan, Xiaoqin; Zhang, Yue; Wang, Xudong

2017-06-01

Black silicon (b-Si) is a surface-nanostructured Si with extremely efficient light absorption capability and is therefore of interest for solar energy conversion. However, intense charge recombination and low electrochemical stability limit the use of b-Si in photoelectrochemical solar-fuel production. Here we report that a conformal, ultrathin, amorphous TiO2 film deposited by low-temperature atomic layer deposition (ALD) on top of b-Si can simultaneously address both of these issues. Combined with a Co(OH)2 thin film as the oxygen evolution catalyst, this b-Si/TiO2/Co(OH)2 heterostructured photoanode was able to produce a saturated photocurrent density of 32.3 mA cm-2 at an external potential of 1.48 V versus reversible reference electrode (RHE) in 1 M NaOH electrolyte. The enhanced photocurrent relative to planar Si and unprotected b-Si photoelectrodes was attributed to the enhanced charge separation efficiency as a result of the effective passivation of defective sites on the b-Si surface. The 8-nm ALD TiO2 layer extends the operational lifetime of b-Si from less than half an hour to four hours.

Optical anomaly in artificial cubic hieratite, K2[SiF6

NARCIS (Netherlands)

Göbel, Ole; ten Elshof, Johan E.; Kaminsky, W.; Hannss, M.

2015-01-01

Crystals of K2[SiF6] were grown in agar gel, silica gel and jelly. Crystals grown in agar gel or jelly exhibit birefringence and consist of six double refracting growth sectors, each having the shape of a tetragonal pyramid. Nevertheless, the structure of the crystals from agar gel could be refined

Thermally Stable TiO2 - and SiO2 -Shell-Isolated Au Nanoparticles for In Situ Plasmon-Enhanced Raman Spectroscopy of Hydrogenation Catalysts.

Science.gov (United States)

Hartman, Thomas; Weckhuysen, Bert M

2018-03-12

Raman spectroscopy is known as a powerful technique for solid catalyst characterization as it provides vibrational fingerprints of (metal) oxides, reactants, and products. It can even become a strong surface-sensitive technique by implementing shell-isolated surface-enhanced Raman spectroscopy (SHINERS). Au@TiO 2 and Au@SiO 2 shell-isolated nanoparticles (SHINs) of various sizes were therefore prepared for the purpose of studying heterogeneous catalysis and the effect of metal oxide coating. Both SiO 2 - and TiO 2 -SHINs are effective SHINERS substrates and thermally stable up to 400 °C. Nano-sized Ru and Rh hydrogenation catalysts were assembled over the SHINs by wet impregnation of aqueous RuCl 3 and RhCl 3 . The substrates were implemented to study CO adsorption and hydrogenation under in situ conditions at various temperatures to illustrate the differences between catalysts and shell materials with SHINERS. This work demonstrates the potential of SHINS for in situ characterization studies in a wide range of catalytic reactions. © 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

Thermal degradation of TiO2 nanotubes on titanium

Science.gov (United States)

Shivaram, Anish; Bose, Susmita; Bandyopadhyay, Amit

2014-10-01

The objective of this research was to study thermal degradation behavior of TiO2 nanotubes on titanium (Ti). TiO2 nanotubes were grown via anodization method on commercially pure Ti (Cp-Ti) discs using two different electrolytes, 1 vol. % HF in deionized (DI) water and 1 vol. % HF + 0.5 wt. % NH4F + 10 vol. % DI water in ethylene glycol, to obtain nanotubes with two different lengths, 300 nm and 950 nm keeping the nanotube diameter constant at 100 ± 20 nm. As grown TiO2 nanotubes were subjected to heat treatment to understand thermal degradation as a function of both temperature and hold time. The signs of degradation were observed mainly when amorphous nanotubes started to crystallize, however the crystallization temperature varied based on TiO2 nanotubes length and anodizing condition. Overall, 300 nm nanotubes were thermally stable at least up to 400 °C for 12 h, while the 950 nm long nanotubes show signs of degradation from 400 °C for 6 h only. Clearly, length of nanotubes, heat treatment temperature as well as hold times show influence toward degradation kinetics of TiO2 nanotubes on titanium.

Nanoparticulate anatase TiO2 (TiO2 NPs) upregulates the expression of silkworm (Bombyx mori) neuropeptide receptor and promotes silkworm feeding, growth, and silking.

Science.gov (United States)

Ni, Min; Zhang, Hua; Li, Fan Chi; Wang, Bin Bin; Xu, Kai Zun; Shen, Wei De; Li, Bing

2015-06-01

Bombyx mori orphan G protein-coupled receptor, BNGR-A4, is the specific receptor of B. mori neuropeptide F (BmNPFR, neuropeptide F designated NPF). BmNPFR binds specifically and efficiently to B. mori neuropeptides BmNPF1a and BmNPF1b, which activates the ERK1/2 signaling pathway to regulate B. mori food intake and growth. Titanium dioxide nanoparticles (TiO2 NPs) can promote B. mori growth. However, whether the mechanisms of TiO2 NPs' effects are correlated with BmNPFR remains unknown. In this study, the effects of TiO2 NPs (5mg/L) feeding and BmNPFR-dsRNA injection on B. mori food intake and growth were investigated; after TiO2 NPs treatments, B. mori food intake, body weight, and cocoon shell weight were 5.82%, 4.64%, and 9.30% higher, respectively, than those of controls. The food intake, body weight, and cocoon shell weight of the BmNPFR-dsRNA injection group were reduced by 8.05%, 6.28%, and 6.98%, respectively, compared to the control. After TiO2 NPs treatment for 72h, the transcriptional levels of BmNPFR, BmNPF1a, and BmNPF1b in the midgut were 1.58, 1.43, and 1.34-folds, respectively, of those of the control, but 1.99, 2.26, and 2.19-folds, respectively, of the BmNPFR-dsRNA injection group; the phosphorylation level of MAPK was 24.03% higher than the control, while the phosphorylation level of BmNPFR-dsRNA injection group was 71.00% of control. The results indicated that TiO2 NPs affect B. mori feeding and growth through increasing the expression of BmNPFR. This study helps clarify the roles of BmNPF/BmNPFR system in TiO2 NPs' effects on B. mori feeding, growth, and development. Copyright © 2015 Elsevier Inc. All rights reserved.

Ferroelectric properties of sandwich structured (Bi, La)4T3O12/Pb(Zr, Ti)O3/ (Bi, La)4Ti3O12 thin films on Pt/Ti/SiO2/Si substrates

International Nuclear Information System (INIS)

Bao Dinghua; Wakiya, Naoki; Shinozaki, Kazuo; Mizutani, Nobuyasu

2002-01-01

Sandwich structured (Bi, La) 4 Ti 3 O 12 /Pb(Zr, Ti)O 3 /(Bi, La) 4 Ti 3 O 12 thin films were fabricated on Pt/Ti/SiO 2 /Si substrates, with the intention of simultaneously utilizing the advantages of both (Bi, La) 4 Ti 3 O 12 (BLT) and Pb(Zr, Ti)O 3 (PZT) thin films such as non-fatigue behaviours of BLT and good ferroelectric properties of PZT. Both BLT and PZT layers were prepared by a chemical solution deposition technique. The experiments demonstrated that the sandwich structure showed fatigue-free characteristics at least up to 10 10 switching bipolar pulse cycles under 8 V and excellent retention properties. The sandwich structured thin films also exhibited well-defined hysteresis loops with a remanent polarization (2P r ) of 8.8 μC cm -2 and a coercive field (E c ) of 47 kV cm -1 . The room-temperature dielectric constant and dissipation factor were 210 and 0.031, respectively, at a frequency of 100 kHz. These results suggest that this sandwich structure is a promising material combination for ferroelectric memory applications. (author)

Irradiation damages in Ti3SiC2

International Nuclear Information System (INIS)

Nappe, J.C.; Grosseau, Ph.; Guilhot, B.; Audubert, F.; Beauvy, M.

2007-01-01

Carbides, by their remarkable properties, are considered as possible materials (fuel cans) in reactor of generation IV. Among those studied, Ti 3 SiC 2 is particularly considered because it joins both the ceramics and metals properties. Nevertheless, its behaviour under irradiation is not known. Characterizations have been carried out on samples irradiated at 75 MeV krypton ions. They have revealed that TiO 2 (formed at the surface of Ti 3 SiC 2 ) is pulverized by the irradiation and that the crystal lattice of Ti 3 SiC 2 dilates with c. (O.M.)

TiO 2 Thin Films Prepared via Adsorptive Self-Assembly for Self-Cleaning Applications

KAUST Repository

Xi, Baojuan

2012-02-22

Low-cost controllable solution-based processes for preparation of titanium oxide (TiO 2) thin films are highly desirable, because of many important applications of this oxide in catalytic decomposition of volatile organic compounds, advanced oxidation processes for wastewater and bactericidal treatments, self-cleaning window glass for green intelligent buildings, dye-sensitized solar cells, solid-state semiconductor metal-oxide solar cells, self-cleaning glass for photovoltaic devices, and general heterogeneous photocatalysis for fine chemicals etc. In this work, we develop a solution-based adsorptive self-assembly approach to fabricate anatase TiO 2 thin films on different glass substrates such as simple plane glass and patterned glass at variable compositions (normal soda lime glass or solar-grade borofloat glass). By tuning the number of process cycles (i.e., adsorption-then-heating) of TiO 2 colloidal suspension, we could facilely prepare large-area TiO 2 films at a desired thickness and with uniform crystallite morphology. Moreover, our as-prepared nanostructured TiO 2 thin films on glass substrates do not cause deterioration in optical transmission of glass; instead, they improve optical performance of commercial solar cells over a wide range of incident angles of light. Our as-prepared anatase TiO 2 thin films also display superhydrophilicity and excellent photocatalytic activity for self-cleaning application. For example, our investigation of photocatalytic degradation of methyl orange indicates that these thin films are indeed highly effective, in comparison to other commercial TiO 2 thin films under identical testing conditions. © 2012 American Chemical Society.

Recubrimientos meso-porosos de SiO2-TiO2-P2O5 para aplicaciones en pilas de combustible de intercambio protónico

Directory of Open Access Journals (Sweden)

Castro, Y.

2014-08-01

Full Text Available The article describes the preparation of mesoporous SiO2-TiO2-P2O5 coatings by Sol-Gel process combined to EISA method for using as proton exchange membranes fuel cells. Tetraethylorthosilicate (TEOS, methyl triethoxysilane (MTES, titanium tetrachloride (TiCl4 and phosphorus trichloride (PCl3 have used as precursors and cetyl trimethylammonium bromide (CTAB as porous generator agent. Films were deposited by immersion technique controlling the relative humidity at 40 and 20-70% and treated at 400 to 500° C for 15, 30, 45 and 60 min. The variation of the refractive index and thickness have studied as a function of temperature and sintering time as well as the pore volume and density of the coatings by spectroscopic ellipsometry. Moreover, the hydrophobic/hydrophilic character of the coatings has been studied by Transform Infrared Spectroscopy (FTIR and by contact angle measurements, following the loss of methyl groups with the temperature and sintering time. The results show that these parameters are crucial to obtain coatings with high porosity and low contact angle, important to obtain high proton conductivity conditions. The sintering conditions were fixed to 400°C / 60 min. Conductivity measurements at four points show high proton conductivity, 0,16 and 0,85 S/cm, up and down ramp, respectively, at 80°C and 80 % of humidity. These coatings are good candidates for PEMFC membranes, if they are deposited onto electrodes.El artículo describe la preparación de recubrimientos mesoporosos de SiO2-TiO2-P2O5 por el método sol-gel combinado con el método EISA para su aplicación como membranas en pilas de intercambio protónico. Se han utilizado como precursores el tetraetilortosilicato (TEOS, metil-trietoxi-silano (MTES, tetracloruro de titanio (TiCl4 y el tricloruro de fosforo (PCl3 y como agente generador de porosidad el bromuro de cetil trimetilamonio (CTAB. Los recubrimientos se depositaron mediante la técnica de inmersión controlando la

Synthesis of highly ordered TiO2 nanotube in malonic acid solution by anodization.

Science.gov (United States)

Ryu, Won Hee; Park, Chan Jin; Kwon, Hyuk Sang

2008-10-01

We synthesized TiO2 nanotube array by anodizing in a solution of malonic acid (HOOCCH2COOH) and NH4F, and analyzed the morphology of the nanotube using scanning electron microscopy (SEM). The morphology of TiO2 nanotube was largely affected by anodizing time, anodizing voltage, and malonic acid concentration. With increasing the anodizing voltage from 5 V to 20 V, the diameter of TiO2 nanotube was increased from about 20 nm to 110 nm and its length from about 10 nm to 700 nm. In addition, the length of TiO2 nanotube was increased with increasing anodizing time up to 6 h at 20 V. We obtained the longest and the most highly ordered nanotube structure when anodizing Ti in a solution of 0.5 wt% NH4F and 1 M malonic acid at 20 V for 6 h.

Influence of SiO2 Addition on Properties of PTFE/TiO2 Microwave Composites

Science.gov (United States)

Yuan, Ying; Wang, Jie; Yao, Minghao; Tang, Bin; Li, Enzhu; Zhang, Shuren

2018-01-01

Composite substrates for microwave circuit applications have been fabricated by filling polytetrafluoroethylene (PTFE) polymer matrix with ceramic powder consisting of rutile TiO2 ( D 50 ≈ 5 μm) partially substituted with fused amorphous SiO2 ( D 50 ≈ 8 μm) with composition x vol.% SiO2 + (50 - x) vol.% TiO2 ( x = 0, 3, 6, 9, 12), and the effects of SiO2 addition on characteristics such as the density, moisture absorption, microwave dielectric properties, and thermal properties systematically investigated. The results show that the filler was well distributed throughout the matrix. High dielectric constant ( ɛ r > 7.19) and extremely low moisture absorption (ceramic particles served as barriers and improved the thermal stability of the PTFE polymer, retarding its decomposition. The temperature coefficient of dielectric constant ( τ ɛ ) of the composites shifted toward the positive direction (from - 309 ppm/°C to - 179 ppm/°C) as the SiO2 content was increased, while the coefficient of thermal expansion remained almost unchanged (˜ 35 ppm/°C).

Optical Properties and Photoactivity of The Pigmentary TiO2 Doped with P2O5, K2O, Al2O3 and Sb2O3

International Nuclear Information System (INIS)

Glen, M; Grzmil, B

2011-01-01

The influence of the increasing content of antimony calculated to Sb 2 O 3 (0.08-0.57 mol%) with the constant amount of the other additives (calculated to P 2 O 5 , K 2 O, Al 2 O 3 ) on the optical properties and photostability of doped rutile has been investigated. The properties of the obtained TiO 2 -PKAlSb samples were compared to the commercial TiO 2 -PKAl composition. The starting material was the concentrated suspension of technical-grade hydrated titanium dioxide (HTD). The dopant agents' solutions were introduced to HTD. Prepared samples were calcined with gradually increasing process temperature. The XRD analysis was used to determine the rutile content in the TiO 2 samples. Optical properties of modified titanium dioxide have been determined spectrophotometrically by measuring the colour in the white (brightness, white tone) and grey system (relative lightening power, grey tone). Photostability was characterized by the white lead-glycerin test with UV-Vis light. It was observed that with the increasing content of antimony in rutile TiO 2 , doped with phosphates, potassium and aluminium, the brightness and grey tone were increasing but white tone decreased. The changes of the relative lightening power values were insignificant. Comparing the samples of TiO 2 -PKAlSb with the TiO 2 -PKAl composition it was observed that titanium dioxide doped with antimony had better white and grey tone. The increasing Sb 2 O 3 content in the TiO 2 caused the improvement of the photostability.

Experimental measurement and modelling of reactive species generation in TiO2 nanoparticle photocatalysis.

Science.gov (United States)

Turolla, Andrea; Piazzoli, Andrea; Budarz, Jeffrey Farner; Wiesner, Mark R; Antonelli, Manuela

2015-07-01

The generation of reactive species in titanium dioxide (TiO 2 ) nanoparticle photocatalysis was assessed in a laboratory scale setup, in which P25 Aeroxide TiO 2 suspensions were photoactivated by means of UV-A radiation. Photogenerated holes and hydroxyl radicals were monitored over time by observing their selective reaction with probe compounds, iodide and terephthalic acid, respectively. TiO 2 aggregate size and structure were characterized over the reaction time. Reactive species quenching was then described by a model, accounting for radiative phenomena, TiO 2 nanoparticle aggregation and kinetic reactions. The interaction between iodide and photogenerated holes was influenced by iodide adsorption on TiO 2 surface, described by a Langmuir-Hinshelwood mechanism, whose parameters were studied as a function of TiO 2 concentration and irradiation time. Iodide oxidation was effectively simulated by modelling the reaction volume as a completely stirred two-dimensional domain, in which irradiation phenomena were described by a two-flux model and the steady state for reactive species was assumed. The kinetic parameters for iodide adsorption and oxidation were estimated and successfully validated in a different experimental setup. The same model was adapted to describe the oxidation of terephthalic acid by hydroxyl radicals. The kinetic parameters for terephthalic acid oxidation were estimated and validated, while the issues in investigating the interaction mechanisms among the involved species have been discussed. The sensitivity of operating parameters on model response was assessed and the most relevant parameters were highlighted.